I have heard mostly bad news on gas mileage of motorcycles, mopeds, scooters, etc... As in with most fairly good cases the sub-car gasoline-powered vehicle has gas mileage only a little better than that of cars that get good gas mileage.
Reasons:
- Smaller/lighter gasoline powered vehicles often have 2-stroke engines, which are significantly less efficient than the 4-stroke engines used in cars and generally in heavier motorcycles.
- Most cars have aerodynamic design that is not used to a similar extent for exposed people on smaller/lighter vehicles. At least this one detracts mainly from highway fuel economy and hardly from urban street fuel economy.
- Smaller, lighter vehicles to some extent lend themselves to less-fuel-economical driving habits. I have seen how a fair amount of people that drive 4-stroke motorcycles drive more like bicycle messengers than car drivers ("cagers") do.
I think that if you get the smallest available 4-stroke motorcycle and drive it as gently as cage drivers usually drive their cages, you would get (MY GUESSTIMATE) about 60 MPG both city and highway, and about 80-90 MPG on country roads cruising at at 40-50 MPH or at whatever speed is hardly outside this range while using a higher gear and having the engine sounding like it is running efficiently. At higher speeds, I see air resistance making motorcycles having fuel economy drop with increasing speed towards only somewhat more than is achievable with better-highway-mileage cars at such higher speeds.
- Don Klipstein ( snipped-for-privacy@misty.com)