Stop at nearly any gas station these days and there’s a good chance you’ll see it: a nozzle labeled “flex fuel.” It may cost less than regular gasoline, too.
What is this flex fuel, and do you want to run it? Judging by the comments we’ve seen online, those seemingly simple questions can cause all kinds of confusion.
What is …
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In other words, ethanol runs "leaner" than gasoline.
I ran a tank of 88 from Sheetz in my 1977 MGB a few years ago while exploring different fuel mixtures. The car ran very well and was cleaner at the exhaust pipe. (This was measured by highly sophisticated equipment; my nose.)
The miles per gallon was lower and the fact that this fuel is "illegal" for my car as well as having only one known source, Sheetz, it didn't make sense to risk potential system deterioration in addition.
Regarding pure or 100% gasoline, my car runs terribly on it. My suspicion is that so little of pure or 100% gasoline is sold from the limited sources available to me, that the fuels are contaminated in some way or become somewhat inert because of age.
So far, premium octane fuels from top-tier fuel stations (Sunoco being one) have produced the best and most consistent results for mileage per tank and smooth running.
Another variable: Without testing a sample, you also don’t know exactly how much ethanol is found in that E85.