# Regular or super ?



## vw_rabbit (Nov 9, 2006)

What do you fill up with, regular or super ? have you notice a valuable difference ? My manual says fill it with regular octane 87, for best performance you may use super .
I know at fisrt the engine was developped with a need for super 91 or 94 for best performance and the compression ratio was at 10:1 .now it as been droped to 9.5:1 , I gues that they didnt want to loose buyers with a need for expensive gas ?


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## AdamVC (Jul 26, 2006)

*Re: Regular or super ? (vw_rabbit)*

I use regular. Never tried it with anything higher.
Based on other people's past comments, you won't notice a big change (in performance or fuel economy) if you use higher octance gas.


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## the.ronin (Feb 22, 2006)

At first I was adamant about using 87 ... consistent reports of higher octane not providing _any_ benefit. Recently I've been putting in 89 and maybe it's just me but I am getting slightly better mileage and the car feels more responsive. I'll probably use 89 more regularly now that gas prices have come down.


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## abqhudson (Jul 22, 2006)

I agree with the.ronin. I've been using the better grade and notice that my Rabbit seems to be more responsive and gets slightly better gas mileage. I think that it's worth the cost.
Jim


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## omni1 (Mar 21, 2006)

*Re: (abqhudson)*

93+, you feel the difference, and I only, ONLY use shell, best gas around


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## @[email protected] (Aug 29, 2003)

I haven't got my Rabbit yet (Arriving Mid Dec) but I always used Sunoco Ultra 94 Octane on my '91 GTi and it made a big impact in both fuel economy and performance. Actually, I think the GTi even "bogs" if I try anything lower then 91...
I'll be feeding nothing but 94 to my new Rabbit when I get it.


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## the.ronin (Feb 22, 2006)

*Re: (omni1)*


_Quote, originally posted by *omni1* »_93+, you feel the difference, and I only, ONLY use shell, best gas around









I wish I had bookmarked this article that came across advising to switch between various leading gas every 3 months or so. The author argued that doing so would serve to prevent buildup of the cleaning additives in the gas. In your case, Shell cleaning additives have likely (according to the author) built up in your car. Since all cleaning additives are different, switching to, say, Chevron would clear out those additives - whilst building up its own. Interesting article and seemed to make sense.
With respect to using 93+ octane ... I'm sure I understand how a naturally aspirated engine could take advantage of the added juice?


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## AdamVC (Jul 26, 2006)

*Re: (the.ronin)*

Hmmm...well maybe there is SOME advantage to using the higher octane gas, question is if it's worth it.
I do remember seeing a post about this previously, tried a quick search, couldn't find it. Maybe it was all in my imagination??








Well, either way, I'm sticking to 87, unless people can give me some hard figures (tracked mpg or 0.5hp gain on the dyno)!!!


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## travis3265 (Nov 15, 2003)

i always use 93. aside from the performance and fuel economy, it burns cleaner and its just overall better for your fuel system and engine in general.


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## Deception (Oct 5, 2000)

*Re: Regular or super ? (vw_rabbit)*

Tried 87, 89, 91 and 92. I did not notice any difference in performance or mileage with higher octane fuel, so I just stuck with what VW recommends: 87 octane.


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## BuddyWh (Nov 11, 2006)

*Re: Regular or super ? (vw_rabbit)*

Hi... I've been loitering a while on this forum, so please bear with me... also, I don't recall seeing an FAQ on this, so pardon me if I've missed it.
In my readings about this, and "in general", using higher octane fuels is only beneficial if the engine needs it. Stated another way: if the engine doesn't need it, it is wasted expense all else being equal.
A little background to my reasoning, so bear with me... 
I'm aware that with a too-low octane fuel the engine will pre-ignite the fuel (or knock) early in the compression cycle. Since that can be damaging modern engines usually have a knock detector: at the onset of knock the engine control computer retards timing to protect the engine. Depending on how much the timing is retarded performance can suffer quite a bit. 
TC's and SC's increase the need for higher octane for the same compression ratio engine. And there are other variables involved: for instance, all else being equal, high altitude reduces the need for higher octane and higher air temperatures can increase the need for higher octane. 
And I'm still learning about VW engine tech (one reason for this long post). For instance: I've no idea how FSI can impact the need for octane! 
If I recall the compression ratio of the 2.5l in my Rabbit is fairly low: around 9.5:1. But the ignition timing could be calibrated for very aggressive advanced timing for emissions control reasons. I assume the 2.5 uses an anti-knock detector... does anybody know for certain how this works in this engine? If it does, it's possible that why the manual states "regular fuel but use higher octane for maximum performance." Even then, I question whether more than mid-grade (89-91) will do anything given the (relatively) low compression of this un-turbo'd engine.
Since performance changes a lot over the first 2-3K miles I'll have to wait a while to make a fair comparison using my butt dyno, but I plan on using a variety of fills. I'll also keep tabs on mileage to check it out even though I kinda lean to the environmental variables, where the driver is part of the environment, swamping effects of octane. Why else would VW start with a baseline recommendation for regular?
Well... that's my thoughts on it and I really am interested in others' experiences with fuel types.


_Modified by BuddyWh at 6:10 AM 11-11-2006_


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## AdamVC (Jul 26, 2006)

*Re: Regular or super ? (BuddyWh)*

Oh, so your second post and you think you know everything?!?!
hehe...just kidding, great write-up, I personally agree.
Let us know how your "tests" turn out.
Oh, and btw, FSI = turbo engine (from MkV GTI, A3, A4, etc.).


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## BuddyWh (Nov 11, 2006)

*Re: Regular or super ? (AdamVC)*


_Quote, originally posted by *AdamVC* »_Oh, so your second post and you think you know everything?!?!

uuuuhhh... not even!!! that's why I gave a little background, so all can see my reasoning and set me straight if it needs some gaps filled.... I'm really curious to know if this all works the same way (aggressive timing, anti-knock sensors, retarded timing at onset of knocking, etc.) with my 2.5 Rabbit. Or does VW use another approach entirely.

_Quote, originally posted by *AdamVC* »_Oh, and btw, FSI = turbo engine (from MkV GTI, A3, A4, etc.).

Isn't FSI direct inject too? Does the injection happen at just the right time for ignition? If so, it seems reasonable that would sidestep the whole problem of pre-ignition. Sorry... this may be off-topic for this forum. Maybe I should be asking in an FSI forum.
But I think you get my point: so much to learn about this new car! AND... it's my first real VW. (I had Fox, but that hardly counts I should think).


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## AdamVC (Jul 26, 2006)

*Re: Regular or super ? (BuddyWh)*


_Quote, originally posted by *BuddyWh* »_
uuuuhhh... not even!!! that's why I gave a little background, so all can see my reasoning and set me straight if it needs some gaps filled.... I'm really curious to know if this all works the same way (aggressive timing, anti-knock sensors, retarded timing at onset of knocking, etc.) with my 2.5 Rabbit. Or does VW use another approach entirely.
Isn't FSI direct inject too? Does the injection happen at just the right time for ignition? If so, it seems reasonable that would sidestep the whole problem of pre-ignition. Sorry... this may be off-topic for this forum. Maybe I should be asking in an FSI forum.
But I think you get my point: so much to learn about this new car! AND... it's my first real VW. (I had Fox, but that hardly counts I should think). 

Yes, FSI is a direct injection turbocharged 2.0L 4-cylinder. Other than that, I'm not too knowledgeable about the technical aspects of that engine.
It's my first VW, although you should count the fox (considering there's a forum for that too -> http://forums.vwvortex.com/zeroforum?id=71)
Oh, and welcome to the vortex!










_Modified by AdamVC at 6:11 PM 11-11-2006_


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## VolksRacer2 (Aug 6, 2002)

*Re: Regular or super ? (AdamVC)*

Not to mention, the Fox was the fatest 1.8 8v car VW offered at the time (assuming you were willing to replace the exhaust downpipe gasket with one that didn't contain the restrictor).
Anyhow, Buddy Wh is dead on in his thinking. Higher octane will not help (and will actually hinder) performance in a vehicle that has no use for it. With a 9.5:1 compression ratio there should rearely be a time when this engine needs anything more than 89 octane. 91 probably wouldn't be that detrimental to performance/economy, but going much beyond that is a complete waste of money and efficiency.
Remember, octane ratings are based on how hard it is to ignite the fuel (higher octane = harder to ignite).


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## coffeeaddict (Aug 28, 2006)

*Re: (the.ronin)*

agreed...i'm getting a bit better mileage using 89 in the last few tanks.


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## BuddyWh (Nov 11, 2006)

*Re: Regular or super ? (VolksRacer2)*


_Quote, originally posted by *VolksRacer2* »_Not to mention, the Fox was the fatest 1.8 8v car VW offered at the time (assuming you were willing to replace the exhaust downpipe gasket with one that didn't contain the restrictor).

When I got it, the Fox just seemed so.... dated... unrefined.. backward even. I couldn't believe it actually had fuel injection (Bosch Jetronic, IIRC, even then a dated mechanical system). I'd read it was built in Brazil and originally intended for that market which explained its lack of sophistication for the time. I just never thought of it as a true VW.
But then... it sure was fun to drive, who'd ever think just 80 hp could do what it did!


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## vw_rabbit (Nov 9, 2006)

*Re: Regular or super ? (BuddyWh)*

Well after a few try , I think , using 87 or 91 is about the same , no difference. people reporting better fuel econ with mid-grade is maybe because that fuel is not the new winterized yet , as mid-grade is the less popular choice.


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## [email protected] (Aug 4, 2005)

BE CAREFUL!!!!- i know in many regions now, shell for example, is blending ethanol into it's premium fuels. although many domestic cars are made to run on this type of fuel (for example they run at a slightly hotter temperature), vw's and most foreign cars were not designed for ethanol. there is some debate as to the time it will take for ethanol blended fuel to harm a non-ethanol prep'd motor, i have heard numbers as little as 2 or 3 tanks.
so just be careful, hopefully someone else will be able to shed a little more light on this.
my .02


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## tagsvags (Nov 25, 2005)

I've been using BP or SHELL premiun since my first tank. No problems so far the Rabbit runs real strong. Time will tell. Just my .02 worth.


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## Deception (Oct 5, 2000)

*Re: ([email protected])*


_Quote, originally posted by *[email protected]* »_vw's and most foreign cars were not designed for ethanol. there is some debate as to the time it will take for ethanol blended fuel to harm a non-ethanol prep'd motor

Nonsense -- Many manufacturers, including VW, allow ethanol blends of up to 10% to be used.
In fact, your owner's manual has a section that covers this. Anything up to E10 is safe to use.


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## [email protected] (Aug 4, 2005)

i am referring to using ethanol @ 15%+ in some regions, i know 10% is supposed to be ok, but read those labels on the pumps, you might be surprised...
-i use 87 oct in my 2.5 mk5, so i hope to be in the clear


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## mujjuman (Jul 29, 2004)

*Re: Regular or super ? (AdamVC)*

i use 87 on the 2.5 and 93 on the VR

_Quote, originally posted by *AdamVC* »_Oh, so your second post and you think you know everything?!?!
hehe...just kidding, great write-up, I personally agree.
Let us know how your "tests" turn out.
Oh, and btw, *FSI = turbo engine* (from MkV GTI, A3, A4, etc.).

not necessarily... non-turbo engines can be FSI too.


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## @[email protected] (Aug 29, 2003)

*Re: Regular or super ? (mujjuman)*

I never put anything less then 94 Octane in my cars. Why? They always drive more refined and crisper when I use better fuel. 87 is garbage comapred to the gold 94 is. So what if you spend the extra $. Fill up on cheaper days and think of it as an expensive day.


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## Deception (Oct 5, 2000)

*Re: Regular or super ? (@[email protected])*


_Quote, originally posted by *@[email protected]* »_I never put anything less then 94 Octane in my cars. Why? They always drive more refined and crisper when I use better fuel. 87 is garbage comapred to the gold 94 is. So what if you spend the extra $. Fill up on cheaper days and think of it as an expensive day.









You're wasting money on 94 octane gas when your car only needs 87. Higher octane does not mean higher quality fuel -- it's only a measure of the fuel's knock resistance.


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## omni1 (Mar 21, 2006)

*Re: Regular or super ? (Deception)*

I was running 87, yuck, you feel a huge difference with 91+, just the way the engine runs and sounds, when your driving believe me you can feel it. cheap gas = http://****************.com/smile/emthdown.gif , especially with a new engine like this.


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## @[email protected] (Aug 29, 2003)

*Re: Regular or super ? (omni1)*


_Quote, originally posted by *omni1* »_I was running 87, yuck, you feel a huge difference with 91+, just the way the engine runs and sounds, when your driving believe me you can feel it. cheap gas = http://****************.com/smile/emthdown.gif , especially with a new engine like this.

Exactly how I feel. I just think of the extra money towards better fuel as a MOD if anything. You def will feel a diff. I ran into a lot of probs with cheap fuel (water, bogging, stalling) and the fuel system will build up with junk quicker too. The higher octane fuels contain more cleaners to keep your engine newer. http://****************.com/smile/emthup.gif


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## 54-46 (Jul 12, 2005)

If your car only requires 87, anything above is wasted and any performance advantage is entirely in your head.


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## @[email protected] (Aug 29, 2003)

*Re: (54-46)*


_Quote, originally posted by *54-46* »_
If your car only requires 87, anything above is wasted and any performance advantage is entirely in your head.


So it's all in our heads, we're all insane? Yep that must be it.
I'm sorry but I don't go through life with only the bare minimum. If that were that case i'd simply eat leaves and drink water for the rest of my life.








I want to fed my car nothing but the cleanest fuel to prolong it's life and give it that extra throttle response. http://****************.com/smile/emthup.gif 
PS: Why do people get quicker 1/4's with higher octane fuel? Surely a Rabbit 2.5 running 87 octane wouldn't get the same 1/4 as lets say 108 octane...










_Modified by @[email protected] at 11:07 AM 12-8-2006_


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## 54-46 (Jul 12, 2005)

*Re: (@[email protected])*


_Quote, originally posted by *@[email protected]* »_
So it's all in our heads, we're all insane? Yep that must be it.


I would've used the term "deluded," or perhaps "biased" if I was feeling friendly.

_Quote, originally posted by *@[email protected]* »_
I'm sorry but I don't go through life with only the bare minimum. If that were that case i'd simply eat leaves and drink water for the rest of my life.










Its not about "minimums," its about what something was engineered for. We'll get to that in a second.

_Quote, originally posted by *@[email protected]* »_
I want to fed my car nothing but the cleanest fuel to prolong it's life and give it that extra throttle response. http://****************.com/smile/emthup.gif 


Its the same stuff, y'know. ITs even the same detergents. Further, octane has nothing to do with being "clean," it has to do with compression, preignition, knocking, and temperature.

_Quote, originally posted by *@[email protected]* »_
PS: Why do people get quicker 1/4's with higher octane fuel? Surely a Rabbit 2.5 running 87 octane wouldn't get the same 1/4 as lets say 108 octane...










Prove it with reliable, provable statistics instead of "this guy posted..."
Your car is designed to run on 87, period. There is some flexibility designed into the system to allow a little wiggle room around this, but overall you won't see better performance, mileage, or less engine wear by putting 93 into your 87. You probably won't see the opposite of this, although the possibility exists. More than anything else, you're wasting your money and natural resources.
_Modified by @[email protected] at 11:07 AM 12-8-2006_[/QUOTE]


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## Deception (Oct 5, 2000)

*Re: (54-46)*


_Quote, originally posted by *54-46* »_
If your car only requires 87, anything above is wasted and any performance advantage is entirely in your head.

http://****************.com/smile/emthup.gif 
You guys can keep [unnecessarily] buying 91/94-octane gasoline for your engine that utterly does not require it... you just make us shareholders invested in oil companies richer.










_Modified by Deception at 12:01 PM 12-8-2006_


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## Deception (Oct 5, 2000)

*Re: (@[email protected])*


_Quote, originally posted by *@[email protected]* »_I want to fed my car nothing but the cleanest fuel to prolong it's life and give it that extra throttle response. http://****************.com/smile/emthup.gif 

Octane has *nothing* to do with the evaluative criteria you mentioned.
Octane is simply a measure of *knock resistance*. Some engines need higher octane to prevent pre-ignition (knock). The 2.5 is *NOT* amongst these engines that require premium gasoline. The 2.5 was engineered to burn -- and operate perfectly on -- 87 octane gas.


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## the.ronin (Feb 22, 2006)

Deception, are there other considerations in the level of octane? I think you hit the nail on the head in regards performance ... but what about engine wear, etc.? No difference to a naturally aspirated engine?
Clearly, additives is a whole separate issue from octane. Presumably, even 87 will contain the same additives from a leading gas station as would its higher octane counterpart. Or is that inaccurate?
Thanks - I myself have opted for 89 whenever I can. No scientific tests but it certainly seems to get me better mileage. Is this all in my head?


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## 54-46 (Jul 12, 2005)

http://en.wikipedia.org/wiki/Octane_rating
"The power output of an engine depends on the energy content of its fuel, and this bears no simple relationship to the octane rating. A common myth amongst petrol consumers is that adding a higher octane fuel to a vehicle's engine will increase its performance and/or lessen its fuel consumption; this is mostly false—engines perform best when using fuel with the octane rating they were designed for and any increase in performance by using a fuel with a different octane rating is minimal."
There's no advantage to a higher octane fuel when your car's engine doesn't require it. 
Save $2 on each fill by buying regular and buy your mom some flowers. She'd really like that.


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## Deception (Oct 5, 2000)

*Re: (the.ronin)*


_Quote, originally posted by *the.ronin* »_Deception, are there other considerations in the level of octane? I think you hit the nail on the head in regards performance ... but what about engine wear, etc.? No difference to a naturally aspirated engine?
Clearly, additives is a whole separate issue from octane. Presumably, even 87 will contain the same additives from a leading gas station as would its higher octane counterpart. Or is that inaccurate?
Thanks - I myself have opted for 89 whenever I can. No scientific tests but it certainly seems to get me better mileage. Is this all in my head?

Basically, higher octane means more knock resistance, and certain engines (ie: High compression ratio; forced induction) will require more knock resistance to perform properly. The 2.5 was engineered with a low CR and is a "basic", relatively "low performance" engine that will run on 87 octane. Running higher octane fuel will not reduce engine wear.
I know that some gas companies advertise "more additives" in the higher octane fuel, but IMO, this is all a marketing ploy. Fuels are made with different octane ratings to suit different knock resistance needs. Some older engines may need higher octane because they are more worn out and may be more prone to ping with low octane gas. You'd be hard-pressed to experience any significant difference from the slightly higher additive content that some gas companies put in their 'premium' gas.
Your higher mileage from using 89 vs. 87 octane could be attributed to many other factors. It's almost impossible to isolate it to simply using 2 octane points higher. My 2.5 got about 4-5mpg better mileage once it past the 10,000 mile mark (probably broken in), for example. That had nothing to do with fuel.
I've ran several tankfuls of various octanes from the same gas station and noticed no difference in power or mileage. I stick with 87 octane because the 2.5 runs totally fine with it.


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## the.ronin (Feb 22, 2006)

*Re: (Deception)*

Thank you sir. http://****************.com/smile/emthup.gif


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## Deception (Oct 5, 2000)

*Re: (the.ronin)*

Unless there's something weird in Californian gas.


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## @[email protected] (Aug 29, 2003)

*Re: (Deception)*

What explains the hundreds of people who always say "It feels more powerful"?
I never said 94 Octane adds power, its just is more responsive. And I don't use 94 for the better response, I mostly use it for the fact that it includes additives that 87 doesn't. I only use Sunoco and they clearly state 94 uses a chemical cleaner thats not used in the other octanes.
Maybe i'm just used to my MKII GTi that requires 91+. I tried 87 on that before and the car just kept stalling. D'oh.


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## Deception (Oct 5, 2000)

*Re: (@[email protected])*


_Quote, originally posted by *@[email protected]* »_What explains the hundreds of people who always say "It feels more powerful"?

Placebo. Or people trying to [falsely] convince themselves that the extra money they [unnecessarily] shelled out bought them something of benefit.


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## abqhudson (Jul 22, 2006)

*Question for "Deception" and "54-46".*

How do you folks square your comments with the study found here:
http://www.pistonheads.com/new...14919
European Tuner tests show that going from 95 octane to 99 octane fuel gives a 5% increase in HP for a Toyota MR2 and a 10% increase for a BMW M3. 
I really doubt that the MR2 required 99 octane fuel. I will tend to trust the data rather than off-the-cuff comments with no back-up. 
Jim


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## Deception (Oct 5, 2000)

*Re: Question for "Deception" and "54-46". (abqhudson)*


_Quote, originally posted by *abqhudson* »_How do you folks square your comments with the study found here:
http://www.pistonheads.com/new...14919
European Tuner tests show that going from 95 octane to 99 octane fuel gives a 5% increase in HP for a Toyota MR2 and a 10% increase for a BMW M3. 
I really doubt that the MR2 required 99 octane fuel. I will tend to trust the data rather than off-the-cuff comments with no back-up. 
Jim

First of all, that is a European measure of knock resistance. (RON)

_Quote »_In most countries (including all of Europe and Australia) the "headline" octane that would be shown on the pump is the RON, but in the United States and some other countries the headline number is the average of the RON and the MON, sometimes called the Anti-Knock Index (AKI), Road Octane Number (RdON), Pump Octane Number (PON), or (R+M)/2. Because of the 8 to 10 point difference noted above, this means that the octane in the United States will be about 4 to 5 points lower than the same fuel elsewhere: *87 octane fuel, the "regular" gasoline in the US and Canada, would be 91-95 (regular) in Europe.*

That test is comparing the use of regular gas vs. premium gas in a car that requires premium. Obviously a BMW M3, which requires premium, would be hindered in performance if you pumped regular gas into it. I have no disagreement there.
In *North American terms*, that test concluded that using 87 octane in a car that needs a minimum of 91 octane results in a 5%-10% loss in power. No surprise there.
Now, that test says absolutely nothing about the corrollary: Using premium gas in an engine that only requires regular (ie: the 2.5). Scientific definitions of "octane" explain that using a higher knock-resistance fuel provides no benefit to engines that do not need such high knock resistance. You are only wasting money.
"Off the cuff" comments? I think not.


_Modified by Deception at 3:59 PM 12-9-2006_


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## BuddyWh (Nov 11, 2006)

*Re: Question for "Deception" and "54-46". (abqhudson)*


_Quote, originally posted by *abqhudson* »_How do you folks square your comments with the study found here:
http://www.pistonheads.com/new...14919
European Tuner tests show that going from 95 octane to 99 octane fuel gives a 5% increase in HP for a Toyota MR2 and a 10% increase for a BMW M3. 
I really doubt that the MR2 required 99 octane fuel. I will tend to trust the data rather than off-the-cuff comments with no back-up. 
Jim

I tried following the link and it seems to be dead...
I could square it like this: there are two scales for measuring octane... the Motor Octane Rating (MON) and the Research Octane Rating (RON) scales. Each are determined in separate ways and generally result in very different "numbers" often 10 or more "points" in difference. To add to the confusion, the one shown on the pumps in the US aren't either... it is the AKI or Antiknock Index and is an average of the RON and MON ratings for the fuel that should, in theory, be pumped.
We in the US expect to use fuel with AKI of 87 for our 2.5l engines. In one of the other two real systems that *could* translate to a rating of 99. So when this European Tuner magazine is giving a move of 95 to 99 they could be quoting RON or MON, whichever is the higher, meaning 85 to 87 AKI, both commonly available regular fuels.


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## Deception (Oct 5, 2000)

*Re: Question for "Deception" and "54-46". (BuddyWh)*

Just read my post above yours.
That European test, which looks at octane numbers in RON units, bascially concluded that by using 87 octane gas in a high-performance engine that needs at least 91 octane, you will see a 5-10% performance hit. NOT anything new.
However, it does not say anything about using 91+ octane in an engine like the 2.5, which was designed to use and only need 87 octane. Performance hit/gain from using premium in the 2.5 = NIL.


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## abqhudson (Jul 22, 2006)

Try This.
http://www.pistonheads.com/new...14919


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## abqhudson (Jul 22, 2006)

For some reason, I can't put the url in.
http://www.pistonheads.com/
news/default.asp?storyId=14919
Try to combine the above. Basically the test shows significant gains with higher octane in both a M3 and older MR2.
Jim
Jim


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## Deception (Oct 5, 2000)

*Re: (abqhudson)*


_Quote, originally posted by *abqhudson* »_Basically the test shows significant gains with higher octane in both a M3 and older MR2.

No. The test shows gains when you use the *proper* octane rating in the M3 and MR2. Both engines needed premium, and by going from regular to premium, the testers saw a gain.
AGAIN, this is *absolutely nothing to do* with using premium in an engine that only requires regular.


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## the.ronin (Feb 22, 2006)

2.5L = naturally aspirated.
The higher = better arguments posed, I believe, are for forced induction engines.
Let's keep things apples to apples please.


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## abqhudson (Jul 22, 2006)

*Deception seems to be a good moniker.*

Deception it is - neither BMW nor Toyota ever recommended/specified a 99 octane fuel for the cars tested in this article. 

Note to readers: just read the article and decide for yourself what it means.
A quote form the article - "It is clear that older engines show a clear benefit of running higher octane fuel, but more modern, sophisticated engines have the ability to advance their fuel timing to take full advantage of this enhancement to a far greater degree. For the BMW M3 CSL the difference between running 95 octane fuel and Tesco 99 fuel was over 40bhp; that’s over 10 per cent. 
So our clear recommendation to those wanting to maximise a car's power is, before even considering a tuning service, is to buy the best fuel." 
I also note that the M3 engine is NA. I'm not sure about the MR2. 
That's all folks - end of my discussion.
Jim


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## Deception (Oct 5, 2000)

*Re: Deception seems to be a good moniker. (abqhudson)*


_Quote, originally posted by *abqhudson* »_Deception it is - neither BMW nor Toyota ever recommended/specified a 99 octane fuel for the cars tested in this article.

*Read my replies!*








Your article is quoting fuel octane in *RON* units (NOT North American units!)
BMW and Toyota specify PREMIUM for these vehicles, which is 99 RON and approximately 91/92 in North America. So that article simply showed that using regular fuel (~95 RON/87 octane) in such vehicles (that require PREMIUM - 99 RON/91 octane) results in a loss of power.
*The test does not SIMPLY conclude that "higher octane = more power".*
Do you even comprehend what I am trying to explain? It's not the jump from 95 to 99 that gave those cars more power. It was simply using the *right fuel*.
Take an M3 in the USA, pump 87 octane into and see what kind of power you make. Then pump 92 into it, and compare. You will see the same results -- the M3 needs 91+ octane.
Holy bejesus










_Modified by Deception at 11:10 AM 12-11-2006_


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## abqhudson (Jul 22, 2006)

More deception.
"BMW and Toyota specify PREMIUM for these vehicles, which is 99 RON and approximately 91/92 in North America."
This statement is simply untrue.


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## Deception (Oct 5, 2000)

*Re: (abqhudson)*


_Quote, originally posted by *abqhudson* »_More deception.
"BMW and Toyota specify PREMIUM for these vehicles, which is 99 RON and approximately 91/92 in North America."
This statement is simply untrue.

Walk down to your local BMW dealership and look at the fuel filler cap on an M3. You will see that the M3 requires premium gasoline, which is minimum 91 octane. (99 octane in *RON* European units.) Both the older E36 and current E46 specify *premium*.
If you pump 87 octane (95 *RON*) into this M3, you will see a significant loss in power, as the test you posted suggested.
Before you start posting again, and using my forum username as a pun, tell me that you grasp the concept of the difference between European RON vs. North American AKI octane ratings.
I'm not here to "deceive" anybody: I'm telling it like it is. Using 91 octane in your 2.5 is wasting money and will not give you any performance benefit. You're just wasting your money.


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## Deception (Oct 5, 2000)

*Re: (Deception)*

Simplified example:
BMW M3 -- Manufacturer requires a minimum of 91 AKI/99 RON octane for optimal performance.
- You fill her up with 87 AKI/95 RON: You see a 5-10% loss in power.
- You fill her up with 91 AKI/99 RON: You regain the 5-10% that was lost due to using the wrong fuel.
Jetta 2.5 -- Manufacturer requires 87 AKI/95 RON octane for optimal performance.
- You fill her up with 87 AKI/95 RON: You get the power that the engine was made to produce.
- You fill her up with 91 AKI/99 RON: You don't see any gain in power over using 87 AKI/95RON.
As you can see, the test shows that using regular gas in a car that needs premium gas causes a loss in power. However, it does not show the opposite of using premium gas in a car that needs regular.
Clear?


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## Deception (Oct 5, 2000)

*Re: (the.ronin)*


_Quote, originally posted by *the.ronin* »_2.5L = naturally aspirated.
The higher = better arguments posed, I believe, are for forced induction engines.
Let's keep things apples to apples please.

Some naturally aspirated engines still require premium. For example, the Honda S2000, Honda Civic Si, BMW M3, Audi S4 4.2, Mercedes-Benz V6s and V8s... etc.
Higher octane does not necessarily mean "better". It all depends on your engine's design. If your engine was designed to require premium (ie: VW 2.0T FSI), then you will see better performance from using 91+ than with 87+. However, some people think that this rule applies to all engines, which is false. If your engine was designed to only need 87 octane, then you will see no benefit from going with a higher octane gasoline.
You can simply look at the design of the 2.5: It only has a 9.x:1 compression ratio and is quite low-tech with a very low redline. This is a prime engine for regular gas: There is nothing special in its engineering that would need premium, nor would it be anywhere close to needing the knock resistance offered from 91+ octane gasoline.


_Modified by Deception at 2:26 PM 12-11-2006_


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## gardner5236 (Jun 19, 2006)

*Re: (Deception)*

We all know that a high compression engine requires high octane fuel and a low compression engine requires at least 87. What is there to debate? The 2.5 is a low compression engine and thus runs perfect on 87 as per the sticker on the fuel door. Why would they put it there if it was not the correct grade? Now, there is nothing wrong with using a higher octane fuel in a low compression engine. What we should be debating is whether or not there is a difference in performance using 87 octane from a mom and pop gas station compared to shell or chevron.


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## huevosrancheros (Dec 13, 2006)

*Re: Regular or super ? (Deception)*


_Quote, originally posted by *Deception* »_
You're wasting money on 94 octane gas when your car only needs 87. Higher octane does not mean higher quality fuel -- it's only a measure of the fuel's knock resistance.


So, true







,
you guys should stop using butt dynos'


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