Quote:
Originally Posted by Hacksaw
I, for one, believe it's completely logical to think one's mpg will increase with higher octane fuel. The opposite has rang true for E85, if I'm not mistaken...
Hacksaw.
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high octane fuel will only increase mpg if your engine needs it to keep from knocking.
the lowest octane your car is made for will have the best milage return.
the additives that keep higher octane from pre combusting under high pressure/heat don't burn as well in a normal engine.
some higher octane fuels claim to help your engine run cleaner but a bottle of fuel injector cleaner when you change your oil will have about the same effect
the reason e85 gives such poor mpg is that it has a lower energy density, as ethanol has less BTU's than regular gasoline.