# Regular vs. Premium--Dyno Test



## Reverendbiker (Jan 29, 2005)

As promised, I have just completed my second dyno test to determine whether the V-6 engine in my 2005 Frontier really makes more power on 93-octane gas than it does on regular. A few weeks ago I ran a dyno test on 87-octane gas for a baseline; next I ran a couple of tanks of premium to allow the ecm to adjust, then I did another dyno test for comparison. For the results and graphs look here:
premium vs. regular dyno test


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## Jason82 (Feb 14, 2005)

Reverendbiker said:


> As promised, I have just completed my second dyno test to determine whether the V-6 engine in my 2005 Frontier really makes more power on 93-octane gas than it does on regular. A few weeks ago I ran a dyno test on 87-octane gas for a baseline; next I ran a couple of tanks of premium to allow the ecm to adjust, then I did another dyno test for comparison. For the results and graphs look here:
> premium vs. regular dyno test


Nice work! Stick with 87.


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## jerryp58 (Jan 6, 2005)

Reverendbiker said:


> As promised, I have just completed my second dyno test to determine whether the V-6 engine in my 2005 Frontier really makes more power on 93-octane gas than it does on regular. A few weeks ago I ran a dyno test on 87-octane gas for a baseline; next I ran a couple of tanks of premium to allow the ecm to adjust, then I did another dyno test for comparison. For the results and graphs look here:
> premium vs. regular dyno test


Actual Real Numbers! Ya gotta love it.

Thanks.


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## Dirk Diggler (Mar 6, 2005)

That makes no sense... perhaps the ECU didn't advance timing for the premium fuel?? I have no idea...

Joe.


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## Radioaktiv (Feb 12, 2004)

great info


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## Reverendbiker (Jan 29, 2005)

Dirk Diggler said:


> That makes no sense... perhaps the ECU didn't advance timing for the premium fuel?? I have no idea...
> 
> Joe.


To tell you the truth, it doesn't surprise me all that much. I've had considerable experience with ecm-controlled vehicles that would back off the timing when a lower-octane fuel was used, but I've never seen the reverse. It appears that Nissan has tuned this engine to achieve at least 265 crank HP (and that looks to be conservative) on 87-octane fuel, and the use of premium won't make a big increase in performance.
I've run many dyno tests on cars and bikes, and I know that there is a margin of error. Correction factors help, but no test is exact. Even assuming that the first test was high and the second test was low, the difference between the two would be very small. My truck runs great, with no sign of knock, on 87-octane gas. If I could pick up 10 RWHP by using premium I might consider shelling out an additional $4 per tank, but for results this close I'll be buying the regular stuff and snickering at the 2005 Tacoma owners.


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## Conner (Nov 11, 2004)

Good work. 
I disagree with your conclusions, though. 
To me it looks like there are significant horsepower gains down at the low end--10 whp at 3500 and even more between there and 3750. I have an automatic and that's where I do most of my driving. To me that's definitely worth it. I mean a $100 intake can get you maybe 5 whp and an exhaust costing several hundred maybe another 5 hp? 
To each his own, I guess.


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## Reverendbiker (Jan 29, 2005)

Conner said:


> Good work.
> I disagree with your conclusions, though.
> To me it looks like there are significant horsepower gains down at the low end--10 whp at 3500 and even more between there and 3750. I have an automatic and that's where I do most of my driving. To me that's definitely worth it. I mean a $100 intake can get you maybe 5 whp and an exhaust costing several hundred maybe another 5 hp?
> To each his own, I guess.


I probably didn't do a very good job of explaining the testing process. You might notice on the graphs that there are no readings below 3300 RPM, and the readings weren't very accurate before 3700 RPM. Auto trans vehicles are just more difficult to test, and since we tested in third gear we had to roll-on really slowly and easily below 3700 to keep it from downshifting and ruining the reading. Above 3700 we could pretty well let the hammer down all the way to 5750, where it shut down. By the way, at that point the rev limiter didn't shut us down but the speed limiter was at 107-108 MPH and that was what kicked in. Believe me, there were no real advantages for the 93-octane tank in the 3500-3750 RPM range. Even if there were, I can't see that a performance enthusiast would pay premium prices to get even 10 HP in such a narrow power range.


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## Conner (Nov 11, 2004)

I'm with you now. I always wondered if it was possible to dyno an automatic.


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## Reverendbiker (Jan 29, 2005)

Conner said:


> I'm with you now. I always wondered if it was possible to dyno an automatic.


Possible, but more difficult. My last truck was a 5-speed--just work it up to 4th, then stand on the throttle. You get a much cleaner graph and more accurate readings on the low end. We tried a run in 2nd gear but it compacted the graph too much. To tell the truth, I'd like to see how much low-end torque these VQ engines have. By the way, you're a neighbor--I'm up in Georgetown.


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## Conner (Nov 11, 2004)

No kidding? I work in Austin but I actually live right up here in Cedar Park. Where do you go to get on the dyno?


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## Reverendbiker (Jan 29, 2005)

Conner said:


> No kidding? I work in Austin but I actually live right up here in Cedar Park. Where do you go to get on the dyno?


I have my dyno work done at Colvin Automotive in Austin. They are nationally known, and were recently featured on an edition of "Overhaulin" when they helped build and dyno-tuned a 1970 GTO for Lance Armstrong. Their dyno operator, Daniel is an ace and has done many tests for me. It's worth going to their shop just to drool over the exotic and performance cars in the garage.


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## 1997XETruck (Mar 11, 2003)

I think the advantages with premium fuel will be more evident in the real world though. Most dyno tests are done with the hood open and lots of cool air flowing into the engine bay. In the real world the hood is closed, and summer temperatures can really get the under hood temperatures up there. When you have high ambinet temperatures you're more likely to get detonation (spark knock) - causing the ECU to redard the timing advance to eliminate it when it detects it via the knock sensors. Of course, that will reduce HP. 

In other words, the advantage of premium fuel may not show up until it's 75F+ outside and the engine is subjected to stop and go traffic.

Heath


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## Reverendbiker (Jan 29, 2005)

1997XETruck said:


> I think the advantages with premium fuel will be more evident in the real world though. Most dyno tests are done with the hood open and lots of cool air flowing into the engine bay. In the real world the hood is closed, and summer temperatures can really get the under hood temperatures up there. When you have high ambinet temperatures you're more likely to get detonation (spark knock) - causing the ECU to redard the timing advance to eliminate it when it detects it via the knock sensors. Of course, that will reduce HP.
> 
> In other words, the advantage of premium fuel may not show up until it's 75F+ outside and the engine is subjected to stop and go traffic.
> 
> Heath


Actually, just the opposite occurs. One of the problems with dyno testing is that successive runs tend to show less power because the engine gets hotter and the cooling fan in an enclosed area just doesn't cool as well as does real-world driving. Underhood temperatures have little or nothing to do with the ecm--it gets 80% of its information from the MAF, which draws air from the outside of the engine compartment. I realize that many people desperately want to believe that using higher octane fuel will add performance to an engine designed to operate on regular, but the fact is that there is absolutely not a shred of evidence that shows it to be true.


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## myoung (Apr 15, 2002)

First off... nice web site... great work, but

dyno conditions could also make the small difference... 

did you run a couple tank fulls before testing? 

I have to question the results...weather that's due to methods, dyno procedure, or the vehicle. not sure.. But it's been shown time and time again higher octanes like 92/93 octane will produce higher numbers than rock bottom 87 octane and even higher returns on race octanes like 100+.

Now of course these differences are highlighted in high performance platforms...

Even if you throw all that out and call it a draw for conversation... Then the premium grade is still better due the refinement process... a lot less particular matter like gums etc... over the long run it makes a big difference.

Also you can't measure MPG on the Dyno


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## myoung (Apr 15, 2002)

Plus I think you're throwing out the lower RPM gains and not really sheding the proper amount of test material showing those areas. You do mention gains in the lower areas, however it's never explained.

99.9% of people drive in those lower rpm ranges, not the peak area. Rarely do average drivers even come close to hitting the rpm cut off area.


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## Reverendbiker (Jan 29, 2005)

myoung said:


> First off... nice web site... great work, but
> 
> dyno conditions could also make the small difference...
> 
> ...


Gee, did you even read the info I posted on my site? Let me address your concerns one at a time:
1. As I stated on the web site, dyno tests do have a margin of error. I use one of the best operators in the country, but any machine can have variances (all runs were SAE corrected for humidity, ambient air temp, and atmospheric pressure). Even allowing for a high reading on the baseline run and a low reading on the 93-octane run the variance would be very small, no more than 3-5%--an amount the average owner couldn't even feel.
2. As stated on the web site, I ran the test with 87-octane then ran several tanks of 93-octane (over 1200 miles, actually) to allow the ecm to adjust.
3. Where has it been shown time and again that premium fuel produces higher horsepower IN AN ENGINE DESIGNED TO RUN ON REGULAR? If you have that info, produce it. I can give you many quality references that show quite the opposite--that using fuel that is higher octane than recommended for an ecm-controlled engine is essentially a waste of money. Sure, 100+ octane is used in performance cars, but the compression and timing demand it. Very few vehicles have an ecm that can actually advance timing to take advantage of fuel higher than recommended; my objective was to see if the VQ40 was one of them.
4. "the premium grade is better due to the refinement process". Where did you get that idea? Oil company ads might have you believe it, but there is nothing inherently superior in premium fuel . SOME premium gasolines contain higher levels of additives, but the government requires that all gasoline sold in the US contains detergent additives. If an owner is concerned about clogged injectors it's much cheaper to add a can of injector cleaner every 6 month or so than to pay an extra $4 per tank for premium gas.
5. "you can't measure MPG on the dyno". Apparently you missed my fuel economy test (see the web site). I carefully compared tanks 93-octane and 87-octane gas in a tightly-controlled test loop for over 2,000 miles. The results? Premium fuel yielded 1.4% better mileage but costs about 10% more--hardly a good trade-off.
I'm not looking to start a quarrel here. I'm an ASE-certified mechanic with over 40 years experience wrenching on performance cars and motorcycles. I hear a load of opinions on the boards but precious little factual evidence; my aim was to provide the best information possible and share it with the other members. If one chooses not to believe it, then that's his prerogative.


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## Reverendbiker (Jan 29, 2005)

myoung said:


> Plus I think you're throwing out the lower RPM gains and not really sheding the proper amount of test material showing those areas. You do mention gains in the lower areas, however it's never explained.
> 
> 99.9% of people drive in those lower rpm ranges, not the peak area. Rarely do average drivers even come close to hitting the rpm cut off area.


Have you read this entire thread? If not, please refer back to response #8. Because the truck is an automatic transmission it is very difficult to get accurate readings in the lower RPMs; comparable runs were available only above 3700 RPM or so. Granted, most street driving is done in lower RPM ranges, but we had no reason to believe that the 93-octane fuel would provide any gains there since it provided no gains anywhere else on the power band.


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## myoung (Apr 15, 2002)

Reverendbiker said:


> 4. "the premium grade is better due to the refinement process". Where did you get that idea? Oil company ads might have you believe it, but there is nothing inherently superior in premium fuel . SOME premium gasolines contain higher levels of additives, but the government requires that all gasoline sold in the US contains detergent additives.


no reason to get rude simply because someone disagrees with you.

To answer, Where do I get this idea from? I get that idea from seeing lab spec sheets almost every day on gasoline blends throught the US.

Yes some brands do contain higher precentages of additives and some brands are less quality. Like every product on the consumer market, some are better than others.

Yes, The federal government does have standards, But some states have higher standards than the Fed standards. Some additives are used regionally not nationally.

I wasn't refering to additives per say.. 
Even so, higher grade gasolines have higher gravities, better Reid vapor pressure readings, less sulpher ppm..etc.etc..... the list goes on as to why at the chemical level the premium gasoline is better. If you've ever seen a break down side by side then you wouldn't argue this point...it's obvious.

I was referring to particulate matter..ie crap in the gasoline.. You don't think that one gasoline brand can sell for 10 cents cheaper because they don't want to make as much profit do you?? of course not..they can sell it cheaper because it's cheaper to produce the lower quality fuel...

I'm not arguing the fact that you obtained these numbers... that's fine.. but there is no way you can show any data to prove the statment "Cheap 87 octane is just as good as high priced premium"


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## myoung (Apr 15, 2002)

Reverendbiker said:


> Granted, most street driving is done in lower RPM ranges, but we had no reason to believe that the 93-octane fuel would provide any gains there since it provided no gains anywhere else on the power band.


In a scientific result you can't just throw that out.. 

I understand it's an automatic and it's difficult to test in that range.. But you have to agree the data is flawed if frequently used areas of the power band are absent.

I actually applauded your website and appreciate the work, but you have to understand this is one test on one vehicle, to make broad statement on all is a bit over reaching.


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## Frank1 (Jan 17, 2004)

This was my experience last year; 


I have made an interesting observation using mid and premium grade fuel on my 04 Pathfinder. On mid grade I averaged 18.8 Mpg and was able to reach 145kmh on a steep long uphill stretch of road that I travel. The following week I filled with premium and averaged 17.8 Mpg and reached 139kmh up the same hill with similiar load and weather conditions. Based on my unscientific research I will be using mid grade and possibily trying regular.


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## Frank1 (Jan 17, 2004)

And this;

I've just ran a tank of regular fuel. 143 kmh up the same hill and 19.1 MPG! Regular fuel has given me the best results. I will be running regular from now on.


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## Reverendbiker (Jan 29, 2005)

myoung said:


> I actually applauded your website and appreciate the work, but you have to understand this is one test on one vehicle, to make broad statement on all is a bit over reaching.


I apologize if my answer appeared to be rude--it was never my intent, and as a minister I don't want to be in the rude business. I was just amazed that you made several statements that indicated that you had not read the information on the site before questioning it. The above quote, for example--what blanket statement did I make? In fact, the final sentence from my web site report is this: "You may draw your own conclusions from this test, but mine are clear; my truck runs very well on 87-octane fuel and no better on the high-priced stuff. With gas prices high and getting higher I'm only too happy to fill 'er up with regular, thank you."
You are correct that this is only one test on one vehicle, but what other tests do we have? At my own expense (considerable, I might add) I paid for tests and shared the information so that other 2005 Frontier owners could make informed decisions. As I said earlier, I have made mine; you are free to make your own.


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## fredjara1 (Mar 8, 2005)

Good Job on the tests. Thanks for making them available Rev. I ran a couple of tanks of 91 (pretty much the highest here on the left coast) and a couple of tanks of the 89. According to the gauge on my speedometer, I got better MI with the lower stuff. Of course the gauge does not measure the exact MPG, but is a good benchmark (this according to my brother who is manager for Nissan Tech Publications). 

Rev, I like your web page. Hey, wife and I have been to your great State a couple of times to watch my son in law play baseball. Couple of times to San Angelo and once to Ft. Worth for the Central League All stars. Probably won't be back for awhile. He signed with the Pirates. Long way from TX!

Best regards.


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## Reverendbiker (Jan 29, 2005)

fredjara1 said:


> Good Job on the tests. Thanks for making them available Rev. I ran a couple of tanks of 91 (pretty much the highest here on the left coast) and a couple of tanks of the 89. According to the gauge on my speedometer, I got better MI with the lower stuff. Of course the gauge does not measure the exact MPG, but is a good benchmark (this according to my brother who is manager for Nissan Tech Publications).
> 
> Rev, I like your web page. Hey, wife and I have been to your great State a couple of times to watch my son in law play baseball. Couple of times to San Angelo and once to Ft. Worth for the Central League All stars. Probably won't be back for awhile. He signed with the Pirates. Long way from TX!
> 
> Best regards.


Hey, Fredjara1--I notice that your truck is very similar to mine. What kind of mileage are you getting? As my '05 Frontier breaks in it seems to be getting better gas mileage--on the latest road trip, all highway, I averaged 22.5 MPG on 87-octane. To my mind that is just incredible for a truck with 265 HP. I have two friends with F150 Ford V-8's and they both get 15-16 on the highway--they're pretty well disgusted when I tell them about my Frontier. Come back to Texas any time! God bless,


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## cryption (Aug 24, 2004)

Reverendbiker said:


> Gee, did you even read the info I posted on my site? Let me address your concerns one at a time:
> 1. As I stated on the web site, dyno tests do have a margin of error. I use one of the best operators in the country, but any machine can have variances (all runs were SAE corrected for humidity, ambient air temp, and atmospheric pressure). Even allowing for a high reading on the baseline run and a low reading on the 93-octane run the variance would be very small, no more than 3-5%--an amount the average owner couldn't even feel.
> 2. As stated on the web site, I ran the test with 87-octane then ran several tanks of 93-octane (over 1200 miles, actually) to allow the ecm to adjust.
> 3. Where has it been shown time and again that premium fuel produces higher horsepower IN AN ENGINE DESIGNED TO RUN ON REGULAR? If you have that info, produce it. I can give you many quality references that show quite the opposite--that using fuel that is higher octane than recommended for an ecm-controlled engine is essentially a waste of money. Sure, 100+ octane is used in performance cars, but the compression and timing demand it. Very few vehicles have an ecm that can actually advance timing to take advantage of fuel higher than recommended; my objective was to see if the VQ40 was one of them.
> ...



good reply!


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## fredjara1 (Mar 8, 2005)

Reverendbiker said:


> Hey, Fredjara1--I notice that your truck is very similar to mine. What kind of mileage are you getting? As my '05 Frontier breaks in it seems to be getting better gas mileage--on the latest road trip, all highway, I averaged 22.5 MPG on 87-octane. To my mind that is just incredible for a truck with 265 HP. I have two friends with F150 Ford V-8's and they both get 15-16 on the highway--they're pretty well disgusted when I tell them about my Frontier. Come back to Texas any time! God bless,



Haven't been on the road with her yet, but I'm working on between 17 and 18 in and around town. My commute to work is 16 miles each way, both freeway and surface street. So I'm not complaining! 

By the way, I'm a "Rev" myself. Spent 9 years as a youth minister, then decided public education needed some missionaries. So there I am now...8th grade. And content to boot!
Fred


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## Reverendbiker (Jan 29, 2005)

fredjara1 said:


> Haven't been on the road with her yet, but I'm working on between 17 and 18 in and around town. My commute to work is 16 miles each way, both freeway and surface street. So I'm not complaining!
> 
> By the way, I'm a "Rev" myself. Spent 9 years as a youth minister, then decided public education needed some missionaries. So there I am now...8th grade. And content to boot!
> Fred


8th grade? Fred, you're a better man than I.......


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## fredjara1 (Mar 8, 2005)

Reverendbiker said:


> 8th grade? Fred, you're a better man than I.......



Don't know about being a better man...remember, I teach 8th grade. And I actually like doing it. I must, this year marks my 31st year of working with that age group! (6 as a volunteer, 9 as a youth pastor, and 16 as a public school teacher). So better?... not. Insane probably  

My 05 Frontier is the LE model, white with the desert tan interior. Only complaint I have is that my AM radio reception is weak. I have the Nismo system, which you probably do too. Also, I wish it had a moon roof. My 00 Frontier had one and I really liked it during the hot months. I could leave it open to help circulate the air when it was in the parking lot.

Another thing I had a hard time adjusting to was the wimpy horn. So I replaced it with a couple from Pep Boys. It doesn't sound like a MAC Truck, but at least it no longer sounds like a Yugo with strep throat!


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## cryption (Aug 24, 2004)

My question is that in the manual it says use 89 octane, the medium, and I was always using tht but just switched to regular. Is there something I can do to get my ECM to be happy on regular?


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## Reverendbiker (Jan 29, 2005)

cryption said:


> My question is that in the manual it says use 89 octane, the medium, and I was always using tht but just switched to regular. Is there something I can do to get my ECM to be happy on regular?


Nope. Please note that my truck is the 2005 Frontier, and my manual specifies a minimum of 87 octane. If your manual specifies 89 octane I wouldn't run anything less.


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## rabbit121 (Mar 10, 2005)

Hey guys.. your thread peeked my interest to try some regular 87 in my pathy. I've always used premuim 91 becasue my VW's never ran right without it, chugging and stalling...they hate 87.. And I've been told the regular will leave more carbon deposits over time..

anywho... today I filled up with some 87 ESSO regular so I could check my milage but I only made it a few KM before I noticed the god awfull gurgling backfiring noise I was getting when I let off the trottle. almost sounded like a hole in my exaust so I was looking for that first... nothing.. happened to have a bottle of octane boot sitting next to me so I dumped it in and voila, only a few seconds before the noise stopped. 

I don't know if I happened to get some water at the pump that worked itself out or something but it was quite a coincidence... 


back to 91 for me...

P.S. my owners manual states 87 or higher aswell...


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## Reverendbiker (Jan 29, 2005)

rabbit121 said:


> Hey guys.. your thread peeked my interest to try some regular 87 in my pathy. I've always used premuim 91 becasue my VW's never ran right without it, chugging and stalling...they hate 87.. And I've been told the regular will leave more carbon deposits over time..
> 
> anywho... today I filled up with some 87 ESSO regular so I could check my milage but I only made it a few KM before I noticed the god awfull gurgling backfiring noise I was getting when I let off the trottle. almost sounded like a hole in my exaust so I was looking for that first... nothing.. happened to have a bottle of octane boot sitting next to me so I dumped it in and voila, only a few seconds before the noise stopped.
> 
> ...


The symptoms you describe don't sound like problems that arise from the use of low-octane fuel, they sound more like use of bad or contaminated fuel. Still, some older vehicles with high miles will require higher octane as deposits build up in the combustion chambers. Best advice is still to use the octane recommended by the manufacturer for your vehicle. If it pings, move up a grade.


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## rabbit121 (Mar 10, 2005)

Well Reverendbiker, and everyone else, I finnished a tank of regular 87 (also worth noting is it was mixed with one bottle of Winns octain boost) and I got an extra 50km+ out of my tank.. this is the best milage I've got yet! 

with supreme 91 I got 12.5 to 13.9 MPG, and on my first tank of regular (with the winns) I got 16.5 MPG!!! 

I filled up with regular again and this time I didn't add the Winns so We'll see what happens this time.


Rabbit


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