The case for motorcycles. Why not use one?

[GasSavers_SD26]

A lot of bikes have the speedo pick up coming off the countershaft sprocket. So, yeah, you'd need a "Speedohealer" to correct it after making changes to the overall gearing. The gearing changes are relatively easy to do.

They are becoming more efficient. More electronics on the ECU, fuel injection is common, but not as sophisitated as on cars, Cats on a lot of bikes.

Still, getting 45MPG on a machine that produces 0-60 times in less than three seconds with quarter mile times less than eleven with a cost of less than $10k. That's your common 600cc sport bike.

A bike's best defense is performance often. When I did street ride, it was important to me to make sure that I was going a little faster than traffic as I could manage better what I was coming upon rather than those that were over taking me, read as attempting to run me over...LOL!

The larger portions of the motorcycle market is cruisers. Standard and "metric"...read Harley-Davidson and the Japanese and other manufacturers. Basically large displacement twins from 1000 t0 1500cc's. There are larger displacement models too, up to 2000cc from Kawasaki, if I remember correctly.

But those aren't bikes that people are buying for economy either.