[Kolyan2k]

Originally Posted by kerm1t

if were talking in terms about 2-3hp gains then sure. but i wouldn't consider that as a real "gain". you will not notice the difference

I have no idea what the official numbers are. With higher octane u also get better MPG so its not just HP

[Meeni]

Originally Posted by Kolyan2k

I have no idea what the official numbers are. With higher octane u also get better MPG so its not just HP

Higher octane is obtained by mixing more octane booster (usually ethanol) which contains less specific energy per volume/mass. So no, you won't even see better MPG.

[Kolyan2k]

Originally Posted by Meeni

Higher octane is obtained by mixing more octane booster (usually ethanol) which contains less specific energy per volume/mass. So no, you won't even see better MPG.

here is article that explains that u do get better MPG

http://www.roadandtrack.com/go/news/...m-fuel-futures

And this is from BMW website: "The performance and fuel consumption rates listed are based on the use of RON 98 fuel"

[bvanlieu]

Originally Posted by Meeni

Higher octane is obtained by mixing more octane booster (usually ethanol) which contains less specific energy per volume/mass. So no, you won't even see better MPG.

With all US gas being 10% ethanol now due to corn subsidies, how can you add more to get a higher octane? I figured the MFGs are blending them lower to meet the necessary minimum octane rating

Toluene and other items help raise the effective octane of the gas.

If the ECM compensates for lower octane but retarding timing a tad and tossing a bit more fuel to proactively prevent detonation, then your MPG can be a few % off.

Its hard to speak in absolutes as different cars will react, well...differently.

- b

[CanAutM3]

Originally Posted by kerm1t

if were talking in terms about 2-3hp gains then sure. but i wouldn't consider that as a real "gain". you will not notice the difference

Dinan tested it on a E46 M3 and gained 11hp going from 91 to 93 octane fuel. That is 4%, certainly not negligibe

Data from a Stock E46 M3

...the stock M3 produced 280 hp (Figure 22- violet line). We then replaced the 91-octane fuel with 93 (available in most parts of the country). The M3′s computer was so quick to determine that the fuel had been improved that it only took four dyno runs for the timing to adapt to the increased octane and raise the power up to 291 hp (Figure 22 – light blue and yellow lines). A gain of 11 hp with just 2 points of octane.

Source: Dinan University

[01ON19]

fwiw

New F80 manual states:

• Maximum ethanol of 10% (satisfying US standard ASTM 4806-xx)
• Recommended fuel grade of AKI 93
• Minimum fuel grade of AKI 91
• "Do not use any gasoline below the minimum fuel grade as this may impair engine performance."

AKI 93 normally corresponds to RON 98 outside North America.

[kerm1t]

Originally Posted by CanAutM3

Dinan tested it on a E46 M3 and gained 11hp going from 91 to 93 octane fuel. That is 4%, certainly not negligibe


Source: Dinan University

thats pretty interesting. wondering if thats consisitant. since every car shows different results, im curious to see how well m235is respond to it.

[kerm1t]

Originally Posted by Meeni

Higher octane is obtained by mixing more octane booster (usually ethanol) which contains less specific energy per volume/mass. So no, you won't even see better MPG.

agreed. in the real world driving, you won't notice much of a different. again, if your talking about a few miles….