True, many of the high powered or large displacement bikes get relatively poor mileage. (in-line 4's of 1000cc get 37-43, Harley's, 40ish, if you're not on the gas). Fuel injection helps, and the fewer cylinders, the better. The insurance on sport bikes and large displacement bikes can be astronomical if you have low experience, low age, or both, enough to negate or debit deeply into any fuel savings. Any bike that gets 50 mpg will still have a reasonable exchange between performance and economy. Enough, I feel, to make up for some of the less than convenient aspects of a motorcycle. Of course, somewhere in that equation is the issue of road rash...or worse.

Smart cars are now being sold where I live. It is a pretty intriguing vehicle, but still "only" 50-55 mpg. You would expect more.