Ummm, what?

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It's no better with other kinds of flex-fuel vehicles, vehicles that can run on E85, 100 percent gasoline, or a combination of the two. Run a two wheel-drive V8 Ford F150 on regular unleaded gas, and the EPA says it'll get 14 mpg city, 19 mpg highway. Run it on E85 ethanol, and it gets 11 mpg city, 14 mpg highway. In other words, fill up on environmentally friendly E85 ethanol, and you'll get fewer miles per gallon than you would on gasoline.

The research octane of ethanol is impressively high, which is a beautiful thing for high-compression and high-boost applications. However, its motor octane (the more extreme standard) is relatively low when compared to racing gasolines of similar (R+M)/2 octane. What this means is that E85 is highly resistant to knock but somewhat sensitive to preignition, comparatively speaking. (Knock and preignition are two different conditions: Knock is spontaneous combustion in the end gases before the flame-front can arrive, while preignition takes place before the timed ignition spark occurs, typically due to localized incandescence or hot spots in the combustion chamber.) But it's no huge deal: Simply know that when running E85 and other ethanol blends, you need to step down one to two heat ranges cooler on the spark plugs, and watch for other potential hot spots such as sharp edges on the piston domes and chambers.