"Ethanol and fuels like E85. 1.5 gallons of ethanol has the same energy content as 1.0 gallon of gasoline. A flex-fuel vehicle will experience about 76% of the fuel mileage MPG when using E85 (85% ethanol) products as compared to 100%gasoline. ... Pure ethanol provides 2/3 of the heat value available in pure gasoline."

This information according to Wikipedia, show we are better off using Non-ethanol gas. My question is it ok to use in our xfires? I can get mid-grade non-ethanol gas, though only rated at 89 0ctane, I had to sign a disclosure, when I bought the car, that said I would not use any gasoline of less than 89 0ctane. Seem we under-value our gas's octane value by 4 or 5 octane points. If I use it, any chance of damage to my car? Any and all comments welcome.

 

Back when I owned my NA Crossfire, I ran the test myself. With normal premium unleaded gas, I experienced a lower MPG but a more responsive throttle due to the higher octane rating. When I decided to chance it with 100% gasoline, I noticed a much better MPG due to it being a "clean gas" but also a less responsive throttle due to the lower octane rating. I liked the result of better MPG, but also missed my very responsive throttle so I continued to run 100% when available but with an octane booster every 3 or so tanks. After adding the octane booster I got both better MPG and my responsive throttle too.

TL;DR - With modern fuel injected engines, you can use either/or just fine without harming anything. Just adjust to your own liking! Good Luck!