I've heard that ethanol blended gas isn't good for your engine, although I've heard no specific problems it causes. Is this just a myth or is there some truth to it? I use it all the time because here ethanol blended gasoline is the same price at 90 octane as regular gasoline at 87 octane.

 

As long as the percentage of ethanol is 5%-10% you are alright, anymore and it will start softening your rubber hoses and rust your internal engine parts. A good trick is to use ethanol on one fill-up and regular gas on the other and keep doing this to re-lubricate the hoses and engine.

 

Ethanol on a modern engine is a non-issue. On older vehicles it will potentially eat the rubber depending on the type used.

However, ethanol while increasing octane will not give much power. Generally, a gasoline formulated with heavier aromatic compounds will have a greater energy value and produce more power. If you use a large amount of ethanol in gasoline you may potentially have to change fuelling (eg mixture).

Ethanol is great for passing emissions testing though.