# 2.5L featured in July European Car Magazine.....



## kfh78 (Dec 25, 2002)

Did anybody see the article in the July issue regarding the 2.5L engine and higher octane gas. I saw it at Barnes and Noble but didn't get to read the enitire article. They tested a stock Jetta (i think it was an '08) on 87oct fuel and dyno'd 137hp. Then they put 91oct fuel and drove the car for 25 miles to let the ecu adapt. The dyno results increased by 7hp and 13tq. These look like whp numbers based on the baseline run. 7whp and 13wtq on a stock motor without chip tuning from simply using higher octane fuel? They also reported smoother throttle response and a slight increase in fuel mileage. This makes me question the need for getting a chip. Anyone else read this article?


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## undercoverdubber (Aug 24, 2008)

if true, interesting.


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## Cherb32 (Jun 18, 2006)

I havnt read it but Ill make a trip to Barnes and Noble today and look for it. Sounds interesting though since I do feel a small difference in throttle response/power with the higher octane (91). I thought it was just me. But yeah if its indeed true then I guess we all need to be chipped:banghead:


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## seanmcd72 (May 14, 2008)

kfh78 said:


> Did anybody see the article in the July issue regarding the 2.5L engine and higher octane gas. I saw it at Barnes and Noble but didn't get to read the enitire article. They tested a stock Jetta (i think it was an '08) on 87oct fuel and dyno'd 137hp. Then they put 91oct fuel and drove the car for 25 miles to let the ecu adapt. The dyno results increased by 7hp and 13tq. These look like whp numbers based on the baseline run. 7whp and 13wtq on a stock motor without chip tuning from simply using higher octane fuel? They also reported smoother throttle response and a slight increase in fuel mileage. This makes me question the need for getting a chip. Anyone else read this article?


If you search the Volkswagenownersclub (Rabbit section) you will find an old post somewheres by a VW tech who scanned a page from a VW factory book/manual that stated clearly that you could run 87octane (it had the Euro numbers which are different) in our 2008 engine with "reduced power" or something like that. The implication was that running 91 or equiv would produce the full amount of power or more than 87... This is one thing that has prevented me from getting chipped. I would to try the C2 chip, but I have always been curious how it would affect this notion...


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## Cabrio60 (Oct 14, 2006)

My 2009 manual states that running premium fuel will yield optimum engine performance. Not sure exactly what the wording means, but it kind of backs up the article.


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## RflxRabbit (Jan 23, 2009)

The car in question is a 2010 Jetta 2.5L six speed auto and it dynoed 133hp @ 5976rpm and 134lb-ft @ 3444rpm stock. Then it was filled up with 91 octane and driven 25 miles. The results were 138hp @ 5908rpm and 146 lb-ft @ 4150rpm. The tester also noted an increase of 1-2mpg, increased throttle response, and smoother power trasitions. The test also included a neuspeed p-flo intake which resulted in 145hp @ 5862rpm and 148lb-ft @4798rpm. I just wanted to post the facts of the article, you draw your own conclusions.


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## tay272 (Aug 22, 2007)

How did the 170hp motor only put down 133 at the wheels? Thats more along the lines of the older 150hp motor isnt it? Im not gettin those numbers completely but its good to have the facts for the article. That's some pretty interesting info.


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## thygreyt (Jun 7, 2009)

it sure is good to know.


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## CostcoPizza (Jan 20, 2008)

I'll be filling up with 93 tomorrow (after running 87 for 20000 miles), I will let you know my observations.


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## [email protected] (Feb 6, 2007)

According to [email protected], the 2.5 head is very prone to pre-ignition (knock).

With that in mind, I guess it might make sense that higher octane fuel would allow for the knock sensor to relax a little and let the ECU call for all the available stock timing


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## Vash350z (Jun 25, 2007)

I wonder if this is true for all years of 2.5L cars.


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## Cabrio60 (Oct 14, 2006)

mac dre said:


> I'll be filling up with 93 tomorrow (after running 87 for 20000 miles), I will let you know my observations.


I filled up yesterday with Shell 93 and have about 75 miles on this tank so far, hopefully enough time for the ECU to adapt. While its still a fresh tank (and this may just be in my head,) the engine is more willing to rev and it seems to pull much smoother. The car was just a tick quicker on the freeway ramp to work today, but the way the engine felt going from 20 to 80 mph was very nice. Fuel economy seemed to improved a small amount too. As prices for gas continue to drop I can easily say I'll fill the car up with 93 more often, it seems to like it and its about $2.50 extra per tank, no worries.

Unfortunately, its very hard to find a station that charges a reasonable price for premium gas, most places in Wisconsin have 91+ for 35 cents a gallon more than 87, and some stations sell 91, some sell 93, and some sell premium with 10% ethanol in it. I had to drive a few miles to find 93 octane with no ethanol that was only 20 cents above regular. While I shouldn't complain, just thought I'd point out some of the hoops a Midwesterner goes through. :beer:


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## thygreyt (Jun 7, 2009)

yesterday i read the manual.

it stated that it can run perfectly fine on 87, but for max engine performance, use 91.

i just dont seem to be able to find 91.. only 87, 89 93


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## CostcoPizza (Jan 20, 2008)

kfh78 said:


> The dyno results increased by 7hp and 13tq.


Let's take a look at the C2 chip, ,

93 Octane
+12hp
+14ft/lbs

Hypothetically, 5 more hp and 1 more tq. (Although the motor dyno'd in Euro Car was pretty weak). So basically an ECU will adjust for 93 and give a tad more power vs just running 93?


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## SocoJoe (Jul 4, 2009)

My car is on E, light will prolly chime on my way home from work tonight. I will fill up with 93 tomorrow and give you my feedback.

Edit**: Wait 91 or 93? lol


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## thygreyt (Jun 7, 2009)

manual says 91


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## SocoJoe (Jul 4, 2009)

Went on my break to get gas and didn't have time to find a gas station with 91, so I just got the norm. I will have to do a little research of the nearest station that carries 91 and try again next fill up.


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## DRGraphix (Jun 7, 2008)

My 05.5 literature also claims peak performance with 91 octane. I experimented a lot for a while, and found better gas mileage with premium. It appeared to take longer to dirty up the tailpipe as well, may have been wishful thinking, tho. I usually push it pretty hard, and I couldn't really say if performance was improved. Will try again.


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## 2ohgti (Nov 8, 2004)

tay272 said:


> How did the 170hp motor only put down 133 at the wheels? Thats more along the lines of the older 150hp motor isnt it? Im not gettin those numbers completely but its good to have the facts for the article. That's some pretty interesting info.


That was because it was an automatic, but even if it was a 5sp, it may not be close to 170hp. It seems not every 2.5 is putting down the same #s. I thought it was pretty interesting to see that there were actual gains w/ higher octaine. I drove my car to almost emty then added 93 octane. It felt a little "peppier" after about 40 miles. The only mod I have is a p-flow, which needs to be cleaned.


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## Cabrio60 (Oct 14, 2006)

They do say the dyno used was notorious for providing lower than normal numbers since its a more accurate portrayal of real world power. Perhaps a Mustang dyno would have given higher numbers that are eye candy to most readers? It is strange because some 08+ Rabbits (5 speed however) have been proven to be in the low to mid 140 whp range bone stock.

Anyways, after a half tank of 93 octane (zero ethanol) with plenty of spirited driving, I can attest that the engine is indeed peppier. More powerful? Butt dyno says yes (warning: may be out of calibration.) What's the most interesting is that the car just ticked to 1/2 tank of gas, and the trip meter reads 254 or so miles, the best ever noted and well into the 30 mpg range. Strange enough is that there's about 25 miles worth of 3rd gear twisty hooliganism and another 50 miles of city driving, so this good mileage is not only new, but welcome. The last tank was on 87 and didn't have spirited driving on it, and was not as good. If premium stays around $2.75 a gallon here, I'm going to keep feeding it and report back, there is a dyno day coming up and maybe I can get concrete numbers on this article's findings. :thumbup:


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## Trench (Nov 20, 2008)

I posted a scan of one of the pages in my manual that said "93 octane was recommend" but it could run on 87.

Basically the 2.5 is a 93 octane engine that has anti-knock sensors which allows 87 to be run.

If I got time later on I will rescan it and post it up.


*Edit*
I think it says 93 in my manual but it may be 91.


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## undercoverdubber (Aug 24, 2008)

gotta be regional, 93 is tuff to find in Socal. 91 is the highest here unless its specialty. 

lol on butt dynoing this. Sh!t, I get +10hp whenever I wax my car, per my butt. 

I think Brad nailed it, higher octane prolly just keeps the knock sensors from retarding the timing under heavy loading.


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## 2ohgti (Nov 8, 2004)

Cabrio60 said:


> They do say the dyno used was notorious for providing lower than normal numbers since its a more accurate portrayal of real world power. Perhaps a Mustang dyno would have given higher numbers that are eye candy to most readers? It is strange because some 08+ Rabbits (5 speed however) have been proven to be in the low to mid 140 whp range bone stock.
> 
> Anyways, after a half tank of 93 octane (zero ethanol) with plenty of spirited driving, I can attest that the engine is indeed peppier. More powerful? Butt dyno says yes (warning: may be out of calibration.) What's the most interesting is that the car just ticked to 1/2 tank of gas, and the trip meter reads 254 or so miles, the best ever noted and well into the 30 mpg range. Strange enough is that there's about 25 miles worth of 3rd gear twisty hooliganism and another 50 miles of city driving, so this good mileage is not only new, but welcome. The last tank was on 87 and didn't have spirited driving on it, and was not as good. If premium stays around $2.75 a gallon here, I'm going to keep feeding it and report back, there is a dyno day coming up and maybe I can get concrete numbers on this article's findings. :thumbup:


 Very true. EC also had a test in Oct. 07' w/ neuspeed chip, tt exhaust, and short ram intake on a 07' 5spd. rabbit w/ 91 octane. The base whp was 138-the same as the 09' auto w/ 91 octaine. I thought that was pretty interesting. I paid $2.95/gallon which is worth it to me, because my car seems to run smoother. I was thinking about getting C2's 87 octane program, but I don't think I will now.


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## tagsvags (Nov 25, 2005)

undercoverdubber said:


> gotta be regional, 93 is tuff to find in Socal. 91 is the highest here unless its specialty.
> 
> lol on butt dynoing this. Sh!t, I get +10hp whenever I wax my car, per my butt.
> 
> I think Brad nailed it, higher octane prolly just keeps the knock sensors from retarding the timing under heavy loading.


 I have used 93 octane in my MK5 2.5 from my first fill. Runs strong and is 100% standard no mods. 
YES the higher octane keeps the knock sensors from retarding the timing and that equals more HP!!!:thumbup:


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## thygreyt (Jun 7, 2009)

i have substancial proof and evedence if the difference... 

i'll post more info tonight. 

i have tried all 3 fuels, and logged fuel comsuotion, power and AFR.


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## JML III (Sep 4, 2007)

My 09 says 87 on the gas door and in the manual. didn't see 91 anywhere. I am trying 91 right now and don't know if I notice a difference.


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## thygreyt (Jun 7, 2009)

ok, so my car... 



mods for thy greyt 
 _ *PERFORMANCE*_ 



*Engine mods* 

:yes: Neuspeed P-Flow 
:yes: neuspeed exhaust 
:yes: neuspeed power pulley 

*SUSPENSION* 


:yes: Stress bar rear (inside trunk) 
:yes: neuspeed rear sway bar 
:yes: Neuspeed Front sway bar 
:yes: RACE springs H&R 2.0" 
:yes: Neuspped rear endlinks 
:yes: BFI Transmission Mount Insert - Stage 2 
:yes: BSH Billet Pendulum Mount 
:yes: NEUSPEED engine torque mount 

--87 oct .. the car was "rough", AFR average of 15.0, about 310 miles per 13 gallons.**good power** "normal vibrations with the stage 2 bfi tranny core mount (28000 miles test) 

--89 oct .. the car is a bit less "rough", afr average of 14.6, 330 miles per 13 gals, "good power", increased vibrations. (500 mile test) 

--93 oct.. the car is a LOT rough-er at low RPM (torque?), but very smooth the rest RPM..... average AFR of 13.8~14.1. 360 miles per 13 gallon. same vibes as 89 oct. 

**butt dyno**


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## 2ohgti (Nov 8, 2004)

Good info. I have found my car to run much smoother on 93 though.


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## thygreyt (Jun 7, 2009)

lo.. i had to edit it... 

i wrote that last night after 15 hours of highway driving, after a 4 hour sleep... 

but yes, def smoother on 93.


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## kungfoojesus (Jan 10, 2005)

The only people who actually log the kind of data we need to prove higher octane = more power are the chip tuners. I somehow doubt they're going to admit you actually get 1hp 5tq from their chip because the car could get 90% of your power gain with just stock settings. 

No wonder they can make 20hp with a chip eh? I have NEVER seen a chip tuner that goes from 93 octane stock to 93 octane chipped. The dyno comparisons are always biased as hell and use 87 stock versus 93 chipped. 

Ever since I installed my CAI I have put premium in my rabbit. I figured the stock ECM was adapting more so than it could with the stock intake to the higher octane fuel. I can say I have gone back and forth quite a bit and definitely notice a big difference shifting hard into second gear and accelerating in third. 

I do log my gas mileage and can tell you I have seen an average increase of 2.3mpg on premium over unleaded. I have also tried the middle grade (91) with no noticeable difference between that and 93 octane. 

My 09 has the different engine management of the newer rabbits, maybe it is smarter or more adaptive. Your results MAY vary.


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