small diameter wheels with taller gearing?
 

Those lowrider jobs where they trade out the standard size wheels for tiny little ones, are those still popular? I'm wondering if you do that (if it's possible to do it without having to get ridiculously fat tires) and at the same time change the differential so the gearing is tall enough to make the engine turn at exactly the same RPMs per MPH as it did before, would that save any gas? I'm thinking it might because this effectively lowers the car, and not for any other reason. So if you also raise the car so that it is the same height as before, then what? Still save a little gas, or not?

If you can change the diff to do that, change the diff and keep the taller tires, :p

That would make a good experiment. Variables would be more fender/tire gap to fill, and ride height

A Festiva has 12" wheels....I got 50.25 mpg my last tank.

Not really. Maybe a really, really, really small change in car aero that could increase in decrease fuel consumption, but that's about it. At a cruise, taller gearing results in better consumption due to lower pumping/friction losses, shorter gearing results in worse consumption due to higher pumping/friction losses, the same would result in the same. :thumbup: