Originally Posted by CUtacomaTIGER
have yall noticed a mpg increase using ethanol free gas? or is difference it very minimal if any? there is a station by me that is always one of the cheaper stations and has ethanol free gas and i was wondering if i should make a point to use it.
It can be significant.
While Ethanol has a base octane rating of 118, making it a cheap octane booster that allows for more timing advance, it is stoich at around 9.5:1 compared to gasoline's 14.:1
If you had two identical engines, one tuned for gasoline and one tuned for ethanol, if the gasoline engine got 29mpg, the pure ethanol engine would get 19mpg, and it would put out 25% less power due to ethanol's lower BTU content.
That's comparing pure gasoline against pure ethanol.
Pump gas is only around 10%, but the computer still needs to add more fuel to compensate for the lean burn.