# 87 vs 93 octane



## 08VWDUB (Feb 1, 2012)

I have 2008 jetta 2.5 100% stock My question is:

When I fill up with 93 the car runs great,has loads of power,and 

starts the second you turn the key.

When I fill up with 87/89 the car still runs like normal,

But the engine seems a bit more raspy,and the car takes a just a tad longer to start,it cranks for a second,with 93 the moment I turn the key it fires up.

Is this from the gas or something else
my battery maybe?


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## Tommy<3vag (Feb 12, 2012)

Could be the higher octane that's making the engine start up quicker. Too many debates about gasoline


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## thygreyt (Jun 7, 2009)

[QUOTE=Tommy


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## Skaffles (May 27, 2011)

08VWDUB said:


> I have 2008 jetta 2.5 100% stock My question is:
> 
> When I fill up with 93 the car runs great,has loads of power,and
> 
> ...


You shouldn't run 93 in your car, in the manual it says you should run 87-91. There are absolutely no benefits for running 93 and can actually be more of a detriment and drag your engine slightly. But yeah gasoline is too controversial lol. :thumbup:


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## Dronks (Jun 7, 2011)

The quicker start up you mentioned is just in your head. The power is also mostly in your head but the higher octane is also limiting knock, leading to more power. Mileage should also be better with higher octane fuels because of less knock and lack of ethanol (depending on where you buy your fuel).


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## Skaffles (May 27, 2011)

Dronks said:


> The quicker start up you mentioned is just in your head. The power is also mostly in your head but the higher octane is also limiting knock, leading to more power. Mileage should also be better with higher octane fuels because of less knock and lack of ethanol (depending on where you buy your fuel).


Yeah most likely in your head, but higher octane burning slower and increasing MPG isn't always true. Sometimes if you put in a higher octane into a car that doesn't require it it might actually take more fuel to com bust which would decrease MPG. And engine knock isn't really an issue with newer cars that you have to always put in higher octane gas.


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## scorch07 (May 17, 2011)

Skaffles said:


> Yeah most likely in your head, but higher octane burning slower and increasing MPG isn't always true. Sometimes if you put in a higher octane into a car that doesn't require it it might actually take more fuel to com bust which would decrease MPG. And engine knock isn't really an issue with newer cars that you have to always put in higher octane gas.


Yeah, I had worse mileage with 93 in mine when it was stock. I haven't tried it since I put my CAI on. That said, engine knock is still a very real problem in engines with high compression, the 2.5L just isn't all that high.


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## rabbitlvr (Oct 8, 2011)

*gas debate*

i run mid grade (89 octane) and my car seems to be running a little rich i.e. exhaust is covered in carbon. is this a result? or could it be something else? or could it be normal of 09 rabbit with tsudo cat back?


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## 2pt5_20v_pwr (Jul 19, 2011)

it is pretty normal for a heavy footed driver to have a lot of carbon buildup on the exhaust tip(s)


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## JohnnyDrama (Feb 15, 2012)

Skaffles said:


> You shouldn't run 93 in your car, in the manual it says you should run 87-91. There are absolutely no benefits for running 93 and can actually be more of a detriment and drag your engine slightly. But yeah gasoline is too controversial lol. :thumbup:


 LOL srsly? :banghead::banghead:


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## Zoolook_ (Mar 17, 2012)

JohnnyDrama said:


> LOL srsly? :banghead::banghead:


 Um, yeah... there is no benefit in this engine (2.5l). 87 - 89 might be marginal, especially in an older engine, but 93 won't add any benefit. 

http://www.imakenews.com/tituswillford/e_article001668469.cfm?x=bgrMmSr,bj1pHjVN,w 

"the octane rating for gasoline has nothing to do with the amount of power locked inside of it – it actually relates to just how much a fuel can be compressed before igniting. The higher the number, the less likely it is to ignite under pressure." 

As someone has already said, the 2.5l doesn't generate an awful lot of compression, so in theory the 93 octane in some circumstances might not fully ignite, which would result in less power and lower MPG. At best, you're simply wasting your money.


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## thygreyt (Jun 7, 2009)

Zoolook_ said:


> Um, yeah... there is no benefit in this engine (2.5l). 87 - 89 might be marginal, especially in an older engine, but 93 won't add any benefit.
> 
> http://www.imakenews.com/tituswillford/e_article001668469.cfm?x=bgrMmSr,bj1pHjVN,w


 lol. 

ignorant people will always be ignorant.


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## Zoolook_ (Mar 17, 2012)

thygreyt said:


> lol.
> 
> ignorant people will always be ignorant.


 ... but but but, enlightenment is merely a click away!


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## thygreyt (Jun 7, 2009)

Zoolook_ said:


> ... but but but, enlightenment is merely a click away!


 give me a stock 2.5 for 1 month, and i'll log it all for you. 

i did it on mine back when i was stock... but a virus killed my laptop with that info... and a whole bunch more.


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## Zoolook_ (Mar 17, 2012)

Log what? Improved performance and mileage with a different octane? 

I am taking a 2,000 round trip next week, so that's 4 - 5 tanks of gas. I'll try and test it myself between 87 and 91.


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## thygreyt (Jun 7, 2009)

Zoolook_ said:


> Log what? Improved performance and mileage with a different octane?
> 
> I am taking a 2,000 round trip next week, so that's 4 - 5 tanks of gas. I'll try and test it myself between 87 and 91.


 
there are different things to log, and mpgs is one of them, timing, and a couple other fields. 

try at least 3 different tanks per fuel octane. Restrain yourself to a brand and octane... say try 87,89 and 93 of Shell. 

optimally, the same fuel station should be used.


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## TylerO28 (Jul 7, 2008)

Oh my God... is everyone in this forum some sort of an idiot? This had been beaten to the ground. And clearly some people have zero idea what they're talking about. I'm astonished by how UN educated people try to make assumptions based on internetz hear say...wrong
Your motor will handle it, it will run better, it will be better for mileage. You will feel a difference.


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## JohnnyDrama (Feb 15, 2012)

Zoolook_ said:


> Um, yeah... there is no benefit in this engine (2.5l). 87 - 89 might be marginal, especially in an older engine, but 93 won't add any benefit.
> 
> http://www.imakenews.com/tituswillford/e_article001668469.cfm?x=bgrMmSr,bj1pHjVN,w
> 
> ...


 LOL srsly? :banghead::banghead: 



TylerO28 said:


> Oh my God... is everyone in this forum some sort of an idiot? This had been beaten to the ground. And clearly some people have zero idea what they're talking about. I'm astonished by how UN educated people try to make assumptions based on internetz hear say...wrong
> Your motor will handle it, it will run better, it will be better for mileage. You will feel a difference.


 I'm pretty sure it's isolated to the 2.5L forum. This thread makes my head hurt.


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## thygreyt (Jun 7, 2009)

JohnnyDrama said:


> LOL srsly? :banghead::banghead:
> 
> 
> 
> I'm pretty sure it's isolated to the 2.5L forum. This thread makes my head hurt.


 agreed...!


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## Zoolook_ (Mar 17, 2012)

TylerO28 said:


> Your motor will handle it, it will run better, it will be better for mileage. You will feel a difference.


 Can you explain, mechanically, how an engine not designed or tuned to take advantage of what is effectively knock resistance, can magically get more power from fuel that has no more power? 

It's all very well you saying the forum is full of idiots, when the only 'evidence' being presented to support what you're saying is anecdotal and subjective. 

I will definitely test this next week though, so I have an open mind on the subject. 

P.S. given that the posts trying to persuade me otherwise contain an abundance of "LOLs", grammatical errors and emoticons, I have my doubts as to whether the posters are even old enough to drive... just sayin' :banghead: :banghead: :banghead:


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## Zoolook_ (Mar 17, 2012)

JohnnyDrama said:


> I'm pretty sure it's isolated to the 2.5L forum. This thread makes my head hurt.


 Well that's because it only applies to the 2.5L... obviously the GTI and R benefit from higher octane fuels. :banghead: :banghead: :banghead:


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## TylerO28 (Jul 7, 2008)

Search the European car article about it. Its been dyno proven to gain. And it gains incredibly well considering its only a few knocks higher. Ask anyone who's been here longer than a month and we all have seen and read the article. Not trying to bash, but I am trying to teach. 
We have been here a while and every once in a great while someone doesn't know the information pertaining to their comments... So we try to teach. An emoticon just shows our frustration with lack of knowledge. I'll dig it up if you'd like to be learned up real Nice! Grammatical error? Yup!


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## thygreyt (Jun 7, 2009)

Zoolook_ said:


> P.S. given that the posts trying to persuade me otherwise contain an abundance of "LOLs", grammatical errors and emoticons, I have my doubts as to whether the posters are even old enough to drive... just sayin' :banghead: :banghead: :banghead:


 first off: the change isnt mechanical... its on the ECU. 

then, age? we just happen to find this funny. 

lastly, johhnyDrama has done LOTS in the dub world. the fact that you know nothing about it means nothing.  

just saying.


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## TylerO28 (Jul 7, 2008)

Besides, the amount of compression on a motor means little when it comes down to it. When you raise octane, you essentially reduce the chance of knock. a motor will knock with lower octane more readily than when using higher octane. Its that simple. Its not like we're taking 120 octane and trying to compress that. Its a few (r+m)/2 over low grade fuel.


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## TylerO28 (Jul 7, 2008)

Proof is right here http://www.europeancarweb.com/tech/proven/epcp_1007_2010_volkwagen_jetta_proven/viewall.html


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## Zoolook_ (Mar 17, 2012)

TylerO28 said:


> Search the European car article about it. Its been dyno proven to gain. And it gains incredibly well considering its only a few knocks higher. Ask anyone who's been here longer than a month and we all have seen and read the article. Not trying to bash, but I am trying to teach.
> We have been here a while and every once in a great while someone doesn't know the information pertaining to their comments... So we try to teach. An emoticon just shows our frustration with lack of knowledge. I'll dig it up if you'd like to be learned up real Nice! Grammatical error? Yup!


 Right, because how long someone has been a member of this forum (and the number of posts as well I suppose) is directly correlated to their knowledge of engineering. Gimme a break... 

I read the European car article about it (the Jetta they tested) and it's compelling I'll admit, which is exactly why I am open minded about it and will definitely try it out.


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## TylerO28 (Jul 7, 2008)

Lol I'll be taking formal apologies, you're rights and I was wrongs via pay pal money transfers....


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## thygreyt (Jun 7, 2009)

Zoolook_ said:


> Right, because how long someone has been a member of this forum (and the number of posts as well I suppose) is directly correlated to their* knowledge of engineering.* Gimme a break...
> 
> I read the European car article about it (the Jetta they tested) and it's compelling I'll admit, which is exactly why I am open minded about it and will definitely try it out.


 dude, engineering knowledge? you are over complicating things. 

and a funny fact: in Engineering school, when you are in design classes, rule number one is: make it simple, stupid!


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## thygreyt (Jun 7, 2009)

so, lets make this simple: 

the engine adjusts timing based on how the sensors reading the engine's performance. 

if the car were to advance the timing, then Knock would occur, and thats not good. when the engine reduces timing, you lose power. 

with 93 oct fuel (less prone to knocking) (read what octane means) the engine can safely run better timing, which nets in better engine performance. 

with Higher RPMs, the engine gets hotter, which could result in pre-detonation. again, better fuel= better performance. 

simple.


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## Zoolook_ (Mar 17, 2012)

TylerO28 said:


> Lol I'll be taking formal apologies, you're rights and I was wrongs via pay pal money transfers....


 I'll be driving by your area next week... maybe I'll buy you a beer! :beer:


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## Zoolook_ (Mar 17, 2012)

thygreyt said:


> so, lets make this simple:
> 
> the engine adjusts timing based on how the sensors reading the engine's performance.
> 
> ...


 
That makes sense.


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## thygreyt (Jun 7, 2009)

thats the simple part. you can actually drive and measure/compare the readings of the different sensors and the different fuels. 

again, on the 2.5L speficially, 93 does a difference.


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## Zoolook_ (Mar 17, 2012)

thygreyt said:


> thats the simple part. you can actually drive and measure/compare the readings of the different sensors and the different fuels.
> 
> again, on the 2.5L speficially, 93 does a difference.


 I have read in another forum that to really take advantage of 93 octane, you need to flash the ECU. Do you think that's true?


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## thygreyt (Jun 7, 2009)

yes. 

but also, flashing the ECU does more than just adjust timing. it actually changes a lot of the drivebility, optiomizes AFR, etc. 

the ecu can only adjust so much... so you will see a bennefit with 93, but to get 100 of the bennefit you will need the sw flash


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## JohnnyDrama (Feb 15, 2012)

Zoolook_ said:


> P.S. given that the posts trying to persuade me otherwise contain an abundance of "LOLs", grammatical errors and emoticons, I have my doubts as to whether the posters are even old enough to drive... just sayin' :banghead: :banghead: :banghead:


 You're right...I know nothing and have zero experience within the automotive performance aftermarket or this VAG space :laugh: ...especially because I used LOL and emoticons. :banghead: 



thygreyt said:


> lastly, johhnyDrama has done LOTS in the dub world. the fact that you know nothing about it means nothing.
> 
> just saying.


 :laugh: :thumbup: :heart:


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## DerekH (Sep 4, 2010)

thygreyt said:


> yes.
> 
> but also, flashing the ECU does more than just adjust timing. it actually changes a lot of the drivebility, optiomizes AFR, etc.
> 
> the ecu can only adjust so much... so you will see a bennefit with 93, but to get 100 of the bennefit you will need the sw flash


 And that being said you will need a sw flash to get the full benefits of whatever fuel you are using in a 2.5. Not just 93oct.


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## Zoolook_ (Mar 17, 2012)

JohnnyDrama said:


> You're right...I know nothing and have zero experience within the automotive performance aftermarket or this VAG space :laugh: ...especially because I used LOL and emoticons. :banghead:


 I know how you feel... I also know nothing because I have a low post-count. If this thread goes on for much longer though, I'll be an expert and be able to build my own dragster from a potato and a piece of string. :snowcool:


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## thygreyt (Jun 7, 2009)

Zoolook_ said:


> I know how you feel... I also know nothing because I have a low post-count. If this thread goes on for much longer though, I'll be an expert and be able to build my own dragster from a potato and a piece of string. :snowcool:


 the thing isnt post count or anything else. 

again, it was the comments, assumptions and knowledge what made some people look bad.


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## TylerO28 (Jul 7, 2008)

I could care less about post count. Ours just frustrating to see the only safe haven in vortex (2.5 forum) get new people asking the same questions over and over.it want ra knock on you by any means. We all get along in here. Its just when someone newer comes along and argues with us about something we've all tested on our own... You're totally welcome to be a part of our group.its just the argumentative replies...


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## Zoolook_ (Mar 17, 2012)

TylerO28 said:


> I could care less about post count. Ours just frustrating to see the only safe haven in vortex (2.5 forum) get new people asking the same questions over and over.it want ra knock on you by any means. We all get along in here. Its just when someone newer comes along and argues with us about something we've all tested on our own... You're totally welcome to be a part of our group.its just the argumentative replies...


 No worries.


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## thygreyt (Jun 7, 2009)

Most of the time we are all properly behaved people... When we feel the need to rant and internet argue, we venture onto the mkv forums!! Lol

Sent from my HTC Sensation using Tapatalk


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## Zoolook_ (Mar 17, 2012)

thygreyt said:


> Most of the time we are all properly behaved people... When we feel the need to rant and internet argue, we venture onto the mkv forums!! Lol


 I'm heading right there... although I have a MKVI, so they might not like that!


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## jaja123 (Jan 17, 2011)

Im pretty sure the manual recommends premium. I run 93 all the time and I do notice a difference going to 87. I also put down 163whp with just carbonio and 2.25 inch magnaflow and of course 93 octane fuel. And remember the premium fuel has more additives which is what you want(helps clean out injectors etc.


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## Jefnes3 (Aug 17, 2001)

Zoolook_ said:


> Can you explain, mechanically, how an engine not designed or tuned to take advantage of what is effectively knock resistance, can magically get more power from fuel that has no more power?



Easy.

The 2.5L engine as setup in stock form is knock limited.
I.e. even the stock ignition maps could be considered 'aggressive' when using 87 octane.

So: how is more power made running 93?
(Log this with vag-com and you will see)
on 87 knock control will pull timing.
on 93 knock control will pull less/none.

How to test this yourself:
Get vag-com
log blocks 010, 020
do a 'street dyno' run: ~under 2000 to redline run
compare the data between the two fuels.

If you see ZERO knock retard on 87 for the entire run, then going to 93 will gain near nothing.


-Jeffrey Atwood


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## thygreyt (Jun 7, 2009)

Jefnes3 said:


> Easy.
> 
> The 2.5L engine as setup in stock form is knock limited.
> I.e. even the stock ignition maps could be considered 'aggressive' when using 87 octane.
> ...


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## GTIarist (Jan 2, 2010)

*87 vs 93 on MKVI Jetta 2.5L*

I put 93 in my car yesterday for the first time, and indeed there is a noticeable change in acceleration. I don't really know a whole lot about mechanical numbers or anything, but I do know my stock 2.5L Jetta does run differently in 93 also.


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## A1an (Mar 22, 2007)

Glad to see this old thread was bumped. Interesting information.


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## Gunbu (Jan 12, 2012)

I don't think Ive ever seen 93 octane before. Only 87,89,91. What sort of special gas station carries such a thing?


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## 02Jetta (Feb 12, 2002)

East coast gas stations, from what I see carries 87 89 93 octanes. We dont have 91 octanes in NJ/NY area


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## Gunbu (Jan 12, 2012)

Gotcha. Yeah I just googled it too, doesn't look like its available at all in California.


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## GTIarist (Jan 2, 2010)

Yeah, I will not go back to 87. I've been running 91 and 93 ever since I found the change in performance, and I'm happier with the acceleration across the board.

And in Pittsburgh we have 87 89 91 92 (sometimes) and 93.


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## iamgap (Jan 17, 2010)

I am glad I found this thread, and I am going to give it another bump.

I don't know if I am just now noticing it, or they are just now (past month or so) bringing it to my area, but all the pumps have a sticker that says contains up to 10% ethynol. Since I have read in several places that VW highly recommends non-ethynol gas, I started looking for non-ethynol stations. Only one in my area (GOGAS) is listed as non-ethynol, so I go to fill up, and it also has a contains up to 10% ethynol sticker.  I then notice that the 93 octane button has a "no ethynol" sticker on it. Not know whether I should use that high of an octane, I relented and used the 87 octane.

Thanks to what I have read here, my next fillup will be GOGAS 93 Octane. (sorry, guys, I just increased fuel prices 10% by saying that)

I am pretty anal about logging fuel economy (between the cold temps, increased traffic, and ethynol, I have dropped about 4 MPG), so I should be able to tell if there has been a difference. My next fillup should be after the T-Day weekend.


gap


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## rabbitlvr (Oct 8, 2011)

http://cdn.*************.net/instances/400x/24670321.jpg


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## PhAyzoN (Nov 29, 2010)

iamgap said:


> I am glad I found this thread, and I am going to give it another bump.
> 
> I don't know if I am just now noticing it, or they are just now (past month or so) bringing it to my area, but all the pumps have a sticker that says contains up to 10% ethynol. Since I have read in several places that VW highly recommends non-ethynol gas, I started looking for non-ethynol stations. Only one in my area (GOGAS) is listed as non-ethynol, so I go to fill up, and it also has a contains up to 10% ethynol sticker.  I then notice that the 93 octane button has a "no ethynol" sticker on it. Not know whether I should use that high of an octane, I relented and used the 87 octane.
> 
> ...


Gas around my way has been "up to 15%" since before I started driving. My quarter million mile 30V V6 and my 2.5 have never complained.


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## phrog23 (May 12, 2007)

Gunbu said:


> Gotcha. Yeah I just googled it too, doesn't look like its available at all in California.


I'm in Lancaster and I know of 2 stations out here that have 93, and I know of one in I think either Burbank, or N.Hollywood that has one( don't remember exactly where).


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## thygreyt (Jun 7, 2009)

most stations on florida are up to 10% ethanol.


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## stef 4x4 (Jan 8, 2012)

The amount of octane a engine needs depends on: compression ratio, lay out of the combustion chaimber and engine (air) temperature in the combustion chaimber.
Compression ratio is not only a static thing but should also be considered dynamic. That means the more air is coming in the combustion chaimber the higher the dynamic compression ratio will be.
That's the reason why turbo engines normally have a lower static compession ratio than engines without turbo that have the same construction because their dynamic compression ratio is higher. 
Good intercooling lowers air intake temperature and means more cooling (and also more oxygen!) in the combustion chaimber and less change on detonation.
Cams, valve timing and intake- and exhaust construction have also big influence on the amount of air the engine gets.
It's already sayd: the energy amount of perol does not depend on the octane number.
The highest petrol efficienty is only possible with the best front ignition curve.
Under normal circumstances the petrol recommanded by the factory will do but I can imagine a car driven in the mountaines with high outside temperatures runs a bit better on petrol with higher octane. 
Detonation will occure later or not at all and the is engine working with optimum front ignition.


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## Gunbu (Jan 12, 2012)

phrog23 said:


> I'm in Lancaster and I know of 2 stations out here that have 93, and I know of one in I think either Burbank, or N.Hollywood that has one( don't remember exactly where).


Oh really? I work up in Burbank I'll have to keep an eye out.


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## 06jettaSEL (May 24, 2011)

this thread brings the lulz

kid with golf (presumably leased for $179/mo) is trying to justify being cheap on gas by citing stupid random internet articles written by other stupid kids trying to justify being cheap on gas.

i'm glad i always use 93 octane even though everyone on the jettav forums says to use regular (more cheapskates trying to justify being cheap) saying there is no added benefits to 93 vs 87. 

i'm glad the 2.5 forum has more knowledgeable peeps who are more legit than the jetta golf v forums which is just a bunch of kids with gtis talking a lot of shyt.


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## Zoolook_ (Mar 17, 2012)

06jettaSEL said:


> this thread brings the lulz
> 
> kid with golf (presumably leased for $179/mo) is trying to justify being cheap on gas by citing stupid random internet articles written by other stupid kids trying to justify being cheap on gas.
> 
> ...


The "shyt" you mention comes equally from both side, on the internet as a whole (not necessarily this forum). Additionally, people who buy 87 octane are not necessarily "cheapskates" trying to justify being "cheap", they just don't necessarily see a benefit from going with a higher octane and thus higher cost. Generally, when you pay more for something, you want to know you're getting something for that extra money. Besides, there is more fluctuation day to day and brand to brand with gas prices, than there is between 87, 89 and 91. 

My own personal experience has changed my mind on this subject somewhat. On a flat road, cruising at 70mph, usually I get 34 - 36mpg (that's the reading I get) on 87 octane. 36 is pretty much the max on average. On 89 octane, that shoots up to 38.9, over the same conditions. It's always a little higher cruising at high speed, although my average around town doesn't seem to change. I can't explain this, but it has been consistent. If I go up to 91 octane, and I only did this for 2 full tanks as part of a really long road trip (more than 5,000 miles in total - 2 full tanks will get me about 950 miles on the highway) it dropped right down to 32 mpg. What does this mean? Nothing, its not scientific and was just my experience, but I stick to 89 octane now (2011 2,5l Golf).

What I would say though is that the fuel 'quality' is more determined by the brand, than the octane - especially at 91+. Higher octane fuel usually has more ethanol, which means it needs more additives to keep the same 'power' - the quality of those additives can vary from pump to pump and certainly from brand to brand. At 87 octane, the quality of probably the same regardless of brand, although personally I'd rather pump in Shell 87 or BP 87 than some no-name 89 brand elsewhere. That's probably irrational! :facepalm:


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## bobsuncle (Oct 18, 2012)

I get horrible mileage with 93, but it's because the car becomes more fun thereby activating my heavy right foot and slowing the occurrence of my right hand twitch until higher RPMs.


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## stef 4x4 (Jan 8, 2012)

Zoolook_ said:


> The "shyt" you mention comes equally from both side, on the internet as a whole (not necessarily this forum). Additionally, people who buy 87 octane are not necessarily "cheapskates" trying to justify being "cheap", they just don't necessarily see a benefit from going with a higher octane and thus higher cost. Generally, when you pay more for something, you want to know you're getting something for that extra money. Besides, there is more fluctuation day to day and brand to brand with gas prices, than there is between 87, 89 and 91.
> 
> My own personal experience has changed my mind on this subject somewhat. On a flat road, cruising at 70mph, usually I get 34 - 36mpg (that's the reading I get) on 87 octane. 36 is pretty much the max on average. On 89 octane, that shoots up to 38.9, over the same conditions. It's always a little higher cruising at high speed, although my average around town doesn't seem to change. I can't explain this, but it has been consistent. If I go up to 91 octane, and I only did this for 2 full tanks as part of a really long road trip (more than 5,000 miles in total - 2 full tanks will get me about 950 miles on the highway) it dropped right down to 32 mpg. What does this mean? Nothing, its not scientific and was just my experience, but I stick to 89 octane now (2011 2,5l Golf).
> 
> What I would say though is that the fuel 'quality' is more determined by the brand, than the octane - especially at 91+. Higher octane fuel usually has more ethanol, which means it needs more additives to keep the same 'power' - the quality of those additives can vary from pump to pump and certainly from brand to brand. At 87 octane, the quality of probably the same regardless of brand, although personally I'd rather pump in Shell 87 or BP 87 than some no-name 89 brand elsewhere. That's probably irrational! :facepalm:


I am not sure but I think ethanol has a lower energy capacity than petrol.
If I am right it means with more ethanol in the fuel mile average will go down.


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## bobsuncle (Oct 18, 2012)

stef 4x4 said:


> I am not sure but I think ethanol has a lower energy capacity than petrol.
> If I am right it means with more ethanol in the fuel mile average will go down.


Ethanol is 80% or so the energy density of petroleum. That's exactly why its a better fuel for high boost situations.


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## KDM1116 (Nov 19, 2012)

Definitely gonna fill up with 89 next time and try it out myself. If it rides smoother and all ill try 93. Glad I found this forum. 


2011 Jetta SE w/out convienence 2.5L 5 Speed Manual


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## bobsuncle (Oct 18, 2012)

KDM1116 said:


> Definitely gonna fill up with 89 next time and try it out myself. If it rides smoother and all ill try 93. Glad I found this forum.
> 
> 
> 2011 Jetta SE w/out convienence 2.5L 5 Speed Manual


It takes two tanks for the ECU to adjust fully. You'll notice the difference --I guarantee it. The ECU on these cars is pretty high quality so it can basically adjust on the fly.


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## KDM1116 (Nov 19, 2012)

I haven't owned my first VW for more then a week(I know nothing about these cars). I've owned crown Vic's my whole life lol ill fill up twice with 89 and see how she rides!! I used to get 12-15 mpg with my v8. I already see HUGE savings with this jetta. 


2011 Jetta SE w/out convienence 2.5L 5 Speed Manual


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## bobsuncle (Oct 18, 2012)

KDM1116 said:


> I haven't owned my first VW for more then a week(I know nothing about these cars). I've owned crown Vic's my whole life lol ill fill up twice with 89 and see how she rides!! I used to get 12-15 mpg with my v8. I already see HUGE savings with this jetta.
> 
> 
> 2011 Jetta SE w/out convienence 2.5L 5 Speed Manual


A ram air intake will get you a slight bump in mileage as well.

That said, upgrades and fuel only get you an increase in mileage if you can keep you foot off the throttle. Every mod I do seems to motivate me to push the car harder :laugh:


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## KDM1116 (Nov 19, 2012)

bobsuncle said:


> A ram air intake will get you a slight bump in mileage as well.
> 
> That said, upgrades and fuel only get you an increase in mileage if you can keep you foot off the throttle. Every mod I do seems to motivate me to push the car harder :laugh:


I've been looking to get the SRI. What's this I hear about an ecu flash after you run higher octane though?


2011 Jetta SE w/out convienence 2.5L 5 Speed Manual


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## bobsuncle (Oct 18, 2012)

KDM1116 said:


> I've been looking to get the SRI. What's this I hear about an ecu flash after you run higher octane though?
> 
> 
> 2011 Jetta SE w/out convienence 2.5L 5 Speed Manual


"The SRI" isn't a ram air. Its a short runner, and that one won't help your mileage at all because all the 2.5L tuners err on the side of safety with SRI tunes. Your car will run slightly rich afterwards.

A short ram like the pflow won't require a tune, and it WILL improve your mileage if you back up off the throttle. I however lack the ability to back up off said throttle.


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## KDM1116 (Nov 19, 2012)

bobsuncle said:


> "The SRI" isn't a ram air. Its a short runner, and that one won't help your mileage at all because all the 2.5L tuners err on the side of safety with SRI tunes. Your car will run slightly rich afterwards.
> 
> A short ram like the pflow won't require a tune, and it WILL improve your mileage if you back up off the throttle. I however lack the ability to back up off said throttle.


Ohhhh I gotcha. I'm gonna drop my jetta in a few months so I'm kinda turning away from the cold air intake, could you possibly post a link to a website selling a ram intake? Do I have to order a heat shield separately?


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## bobsuncle (Oct 18, 2012)

KDM1116 said:


> Ohhhh I gotcha. I'm gonna drop my jetta in a few months so I'm kinda turning away from the cold air intake, could you possibly post a link to a website selling a ram intake? Do I have to order a heat shield separately?


The Pflow by nuespeed in the cheapest @$200 to $220, has CARB compliance and comes with a heatsheild. A lot of people also like Evolution Motorsports' V Flow which comes with an arguably better heatsheild.

Other people just make their own out of auto store pipe and K&N filters. This is the cheapest way to go.

Any way you go, just replace your stock intake and switch to the best gas you can buy. Both improve performance and mileage if you don't stop it afterwards. The car WILL be louder, but most of us like the sound of an uncorked 2.5L.


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## KDM1116 (Nov 19, 2012)

bobsuncle said:


> The Pflow by nuespeed in the cheapest @$200 to $220, has CARB compliance and comes with a heatsheild. A lot of people also like Evolution Motorsports' V Flow which comes with an arguably better heatsheild.
> 
> Other people just make their own out of auto store pipe and K&N filters. This is the cheapest way to go.
> 
> Any way you go, just replace your stock intake and switch to the best gas you can buy. Both improve performance and mileage if you don't stop it afterwards. The car WILL be louder, but most of us like the sound of an uncorked 2.5L.


I'll definitely look into one of them. Maybe even build my own if I can get a day off work haha. After that I'm gonna look into a deeper toned exhaust.


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## deesul (Jan 3, 2009)

OK, I tried this after I read this thread.

When I first read this, I was thinking, "no way, it's in your head, the octane of gasoline does not add horsepower or make your engine run smoother." I'm a UTI grad, Ford and Jaguar Factory certified, have a few ASE's under my belt, ex technician, and I'm an automotive service advisor by trade. So, my brain tries to think things through intuitively. Then I read the entire thread, the article from euro car magazine, etc.. and thought "hmm there might be something here".

Last weekend I filled up with 91 octane instead of my standard 87, since I don't have 93 here in Cali. I'm about half way through the tank of gas and I honestly feel no difference whatsoever in performance, feel, or how fast the engine starts up. I track all of my fuel ups since the car was brand new, and my fuel economy is right on track (so far) with what it should be for the type of driving I've been doing. I have to say, I'm kind of dissapointed. I was really hoping to experience the kind of difference that the OP was talking about. The engine has run really smooth and quiet since day 1, so I wasn't really expecting it to run even smoother. I have to actually watch my tach as I shift because I can't hear the engine and when it's idling I don't feel it running at all. 

Anyways, I tried it. So far I don't see a difference. That's my input.


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## iamgap (Jan 17, 2010)

deesul said:


> OK, I tried this after I read this thread.
> 
> When I first read this, I was thinking, "no way, it's in your head, the octane of gasoline does not add horsepower or make your engine run smoother." I'm a UTI grad, Ford and Jaguar Factory certified, have a few ASE's under my belt, ex technician, and I'm an automotive service advisor by trade. So, my brain tries to think things through intuitively. Then I read the entire thread, the article from euro car magazine, etc.. and thought "hmm there might be something here".
> 
> ...


^^^^ This.

I tried the 93 non ethenol, and it was just a tad worse than 87 ethenol. I ran a full tank of 93 non-ethenol (mostly to run non-ethenol fuel), and then went back to 87 (potentional - sticker said "May contain") ethenol. I know that temps and stop and go make a large difference in mileage, so I will use my monthly drive the Cars and Coffee - Wilmington. With the 87 ethenol, I averaged about 36.5 MPG (on the accuracy adjusted display) on each trip home. On the ride home, I usually run by myself, and I adhere to the speed limit. I also do a lot of coasting to stops and light acceleration (when traffic allows - don't want to be an ID10T in heavy traffic) when I drive by mtyself. On the drive back, towards the end of a tank od 93 octane, I had to do some serious hypermiling on the last few miles to get the trip average up to 35.5.

Bottom line - for me - 87 E10 > 93. I wish I could find 87 without E10, but that aint happening thanks to the ID10TS running our country. 


gap


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## bobsuncle (Oct 18, 2012)

deesul said:


> OK, I tried this after I read this thread.
> 
> When I first read this, I was thinking, "no way, it's in your head, the octane of gasoline does not add horsepower or make your engine run smoother." I'm a UTI grad, Ford and Jaguar Factory certified, have a few ASE's under my belt, ex technician, and I'm an automotive service advisor by trade. So, my brain tries to think things through intuitively. Then I read the entire thread, the article from euro car magazine, etc.. and thought "hmm there might be something here".
> 
> ...


Second tank is where it happens in my personal experience. There are a slew of dynos to back it up.


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## bobsuncle (Oct 18, 2012)

iamgap said:


> ^^^^ This.
> 
> I tried the 93 non ethenol, and it was just a tad worse than 87 ethenol. I ran a full tank of 93 non-ethenol (mostly to run non-ethenol fuel), and then went back to 87 (potentional - sticker said "May contain") ethenol. I know that temps and stop and go make a large difference in mileage, so I will use my monthly drive the Cars and Coffee - Wilmington. With the 87 ethenol, I averaged about 36.5 MPG (on the accuracy adjusted display) on each trip home. On the ride home, I usually run by myself, and I adhere to the speed limit. I also do a lot of coasting to stops and light acceleration (when traffic allows - don't want to be an ID10T in heavy traffic) when I drive by mtyself. On the drive back, towards the end of a tank od 93 octane, I had to do some serious hypermiling on the last few miles to get the trip average up to 35.5.
> 
> ...


#1 E10 is a MAX of 10% b/c those ID10TS in government offices thought that is was rather BS that the greedy wankers at Big Oil were putting MORE than 10% in without even telling you.

I agree that putting 10% booze in the fuel is BS (though I love E85), but the ethanol BS is b/c Iowa caucuses first. Overzealous catering to a relatively low pop state's personal interests is required in order to be elected president. Swappig out leaders won't fix a broken primary system that gives a minority such an overrepresented ability to shovel their products on us.

#2 Where you get fuel matters. Top tier or bust.

http://www.toptiergas.com/deposit_control.html

#3 Gas isn't 90% petrol. It's lower than that. It's full of detergents and additives on top of the 10% booze. Fuel is incredibly variable, and it's why you really need to find a good station or chain and stick with them.


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## deesul (Jan 3, 2009)

bobsuncle said:


> Second tank is where it happens in my personal experience. There are a slew of dynos to back it up.


I would like to see some of these dynos from a MKVI car, as we've discussed, these have different engine management than the MKV cars. I'm not convinced there is any noticeable difference based on my own experience. I'm back to running 87 octane again, and once again, not a noticeable change from my previous tank.


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## bobsuncle (Oct 18, 2012)

deesul said:


> I would like to see some of these dynos from a MKVI car, as we've discussed, these have different engine management than the MKV cars. I'm not convinced there is any noticeable difference based on my own experience. I'm back to running 87 octane again, and once again, not a noticeable change from my previous tank.



http://www.europeancarweb.com/tech/proven/epcp_1007_2010_volkwagen_jetta_proven/viewall.html


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## deesul (Jan 3, 2009)

I said MK6


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## bobsuncle (Oct 18, 2012)

deesul said:


> I said MK6


All the 2009+ are MAF-less.


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## TylerO28 (Jul 7, 2008)

Um? And that matters why?


Sent from my iPad using Tapatalk HD


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## bobsuncle (Oct 18, 2012)

TylerO28 said:


> Um? And that matters why?
> 
> 
> Sent from my iPad using Tapatalk HD


Engine management is pretty different w/o a MAF


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## thygreyt (Jun 7, 2009)

bobsuncle said:


> Engine management is pretty different w/o a MAF


Shows how much you know about the 2.5.

Sent from my HTC Sensation 4G using Tapatalk 2


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## bobsuncle (Oct 18, 2012)

thygreyt said:


> Shows how much you know about the 2.5.


Ugh...

Your damn hero Jeff said that the 09+ cars are significantly different in the ECU department. Call him and ask if you already forgot...


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## thygreyt (Jun 7, 2009)

I thought you were ignoring me..

Sent from my HTC Sensation 4G using Tapatalk 2


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## TylerO28 (Jul 7, 2008)

The difference is the map measures pressure, its easier to tune a map sensor car because its a simple how much pressure is in the manifold? Ok pulse the injectors this much accordingly.
Maf is a touch more picky, it depends on if its a hot wire maf, vortex, or cold wire (there is another one i believe)
Hot wire, takes heat in a wire, however much air going over that wire to cool it results in the fuel trim going up or down. The more power up to 5v goes into that wire the more it heats. That's why its important to get the correct maf for your setup. Map tune is very much more basic
Its a simple version. Kinda like hammer vs scalpel.

Sent from the bottomless pits of HELL!


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## TylerO28 (Jul 7, 2008)

bobsuncle said:


> Ugh...
> 
> Your damn hero Jeff said that the 09+ cars are significantly different in the ECU department. Call him and ask if you already forgot...


Ecu is not a map sensor lol...
He's probably referring to the encrypting difference and what not

Sent from the bottomless pits of HELL!


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## bobsuncle (Oct 18, 2012)

TylerO28 said:


> The difference is the map measures pressure, its easier to tune a map sensor car because its a simple how much pressure is in the manifold? Ok pulse the injectors this much accordingly.
> Maf is a touch more picky, it depends on if its a hot wire maf, vortex, or cold wire (there is another one i believe)
> Hot wire, takes heat in a wire, however much air going over that wire to cool it results in the fuel trim going up or down. The more power up to 5v goes into that wire the more it heats. That's why its important to get the correct maf for your setup. Map tune is very much more basic
> Its a simple version. Kinda like hammer vs scalpel.
> ...



Newer Tricore ECUs can do everything via ping/knock sensors. They can crunch numbers so much faster that the extra sensors are irrelevant.

BTW the MAF based


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## deesul (Jan 3, 2009)

bobsuncle said:


> All the 2009+ are MAF-less.


There is clearly a MAF on the engine from the article.


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## TrillyPop (Jan 27, 2010)

bobsuncle said:


> IIRC the MAP based 09-10 models are on a newer Bosch ECU than the 07-08 MAF cars. *They're not tunable through the port either*.


Incorrect. Mine was port flashed.


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## A1an (Mar 22, 2007)

Ran quite a few tanks of 93 through my 07 Rabbit using the same gas station, similar driving habits, etc. Zero difference in gas mileage. It also didn't feel as though it idled or pulled any smoother as some have reported with the higher octane gas. I'll stick with the 87 for now.


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## nowosun (Dec 28, 2012)

I'm not a Ph.D. from MIT, nor am I an engineer in Wolfsburg. Thus I will start with the test of the 2010 Jetta from the link

http://www.europeancarweb.com/tech/proven/epcp_1007_2010_volkwagen_jetta_proven/

Look into the graph - assuming all tests are accurate and correct - the red line and blue line start to deviate from 3,500 RPM, and start to show a real difference from 4,000 RPM.

So, if you barely drive above 4,000 RPM, higher octane gas will not provide any performance boost (higher low-end torque). If you are driving a 5-speed manual like I am, 4,000 RPM is 40 MPH in Gear 2 and 70 MPH in Gear 3. So, on most of the highways in the US, the only possible scenario one can take the advantage of the performance boost from higher octane gas is accelerating from 40 MPH to 60 MPH in Gear 2. (Unless your uncle is some police captain)

--------------------------------------------------

Next, MPGs.

Higher octane rating is not equal to higher energy density. In fact, 87 gas has slightly higher energy density than that of 93 gas. Since my MKVI Jetta does recommend 87 gas, it is safe to assume that there is no knocking running on 87 at peak power. I cannot think of a reason why higher octane would provide higher MPG. (Regarding the test - 1 or 2 MPG difference from one tank is not very convincing)


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