Originally Posted by sgoldste01
Yeah, most gas stations around here sell E10 (10% ethanol) gas, which greatly reduces our fuel economy. I can't imagine running E85.
Higher octane rating (resistance to detonation) means higher boost/more timing. In layman's term's, it's less "chemically rich" Meaning it takes more volume to generate the same BTUs as gasoline. However, if you had an engine built specifically to take advantage of the higher detonation threshold, you could achieve a greater mechanical efficiency to compensate for the loss in energy content/volume.
But yes, in a car built for gas it hurts fuel economy. It's a big fat waste of money (and no, it's not cheaper than gas) for most of the public but awesome for race cars.
Lesson over, return to stickers.