93 w/ 10% eth VS. 91 w/o eth???

[GTSLOW]

Fuel question here. If you had to decide to go with 93 Octane that has "up to 10% ethanol" or 91 Octane that didn't have any. What would you use? Which is better?

[wrath]

What are you doing with it?

I'd probably pick the 91, as long as it's a constant 91.

[88Nightmare]

I just use whatever is the highest grade gas for the tbss or my bike. It doesn't matter to me what brand it is. If its 91, 92, or 93, with or without ethanol. Neither of those two vehicles are high enough performance where brand and 1 or 2 octane points will matter. Premium is premium to me. I am sure with a higher performance engine/built up engine, it would make a difference.

[Smokey1226]

actually the ethanol is a natural oxygenator (if thats a word) meaning side by side the 93 with ethanol would make more power solely because of the oxygen. Same thing they are doing with most of the race fuels these days with either adding MTBE (another oxynator) or in areas of the country where they ban MTBE they then use Ethanol.

thats my fun fact!!

Im guessing that if you had just a beater car looking for the best gas mileage you might be able to get just a few more miles out of the 91 w/o but its not worth going out of your way for.

[LIZMO]

actually the ethanol is a natural oxygenator (if thats a word) meaning side by side the 93 with ethanol would make more power solely because of the oxygen. Same thing they are doing with most of the race fuels these days with either adding MTBE (another oxynator) or in areas of the country where they ban MTBE they then use Ethanol.

thats my fun fact!!

Im guessing that if you had just a beater car looking for the best gas mileage you might be able to get just a few more miles out of the 91 w/o but its not worth going out of your way for.

so performance get the highest ocatane? and best mileage get the highest with out ethanol?

[wrath]

so performance get the highest ocatane? and best mileage get the highest with out ethanol?

Ethanol has fewer BTUs in it than gasoline. Gasoline has fewer than diesel. Conventional fuel, for the most part, these days is priced by the BTU.

The higher the octane rating, the more resistant it is to compression ignition (spark knock). The higher the octane rating, the higher the compression, the higher the resistance to heat, the more spark advance.

[Smokey1226]

so performance get the highest ocatane? and best mileage get the highest with out ethanol?
no, not 100% true. To get the best performance you want to find the octane that best suits your application without getting detonation or anything else....but without also going too high of an octane. Too high will also slow you down.

What i ment by the ethanol, is if you had a 93 straight up no ethanol... and a 93 with ethanol 9 times outta 10 the Ethanol 93 will make slightly more power just because of the ethanol being an oxygenator.

The octane itself in fuels doesnt MAKE the power. Its what the octane and the fuel ingredients (race fuels) that allow you to do to take advantage of your cars setup that makes the power. i.e. Pull more timing, run leaner, bigger tune up, more boost ect ect.

But as far as MTBE/Ethanol goes that makes power byself because of basically adding more oxygen to the engine than whats already coming in via your intake. So most times you have to jet up, or add fuel to the fuel map on highly oxygenated fuels (113/Q16) but they are proven to make quite a bit more power over the same fuels (C12/C16) without the oxygen.