The engine runs on BTU content of the gasoline, and the computer adjusts for that. If the gas blends are equal then no ethanol will have a 3% higher BTU content and then give 3% better mileage. It is hard to fill a tank repeatedly within 3%.
But all things are not equal, they start with 84 octane before they add the alcohol. Lower the octane usually the higher the BTU content. So now we are at approx 2 to 2.5%% BTU difference. Brand A of fuel at 87 octane can be 5% higher BTU content than brand B at 87 because of the refinery and the crude type.. So basically you can not tell with any scientific degree of precision. Too much noise in the measurement.
The alcohol is hard on plastic parts, and can corrode some metal parts, it can also separate out and cause issues. And E85 is about 35 to 40% lower BTU content and you can very much see the difference there. So I only avoid it on my outdoor power equipment that does not run all the time.
Rod
But all things are not equal, they start with 84 octane before they add the alcohol. Lower the octane usually the higher the BTU content. So now we are at approx 2 to 2.5%% BTU difference. Brand A of fuel at 87 octane can be 5% higher BTU content than brand B at 87 because of the refinery and the crude type.. So basically you can not tell with any scientific degree of precision. Too much noise in the measurement.
The alcohol is hard on plastic parts, and can corrode some metal parts, it can also separate out and cause issues. And E85 is about 35 to 40% lower BTU content and you can very much see the difference there. So I only avoid it on my outdoor power equipment that does not run all the time.
Rod