Check your tire pressure

[Loren Booda]

I had my car tires inflated by 10-20%, and my mileage (mostly city) went from 22.5 to 25 mpg. Does this sound feasible?

[berkeman]

Yes. The downside is increased asymmetric tire wear, with the middle wearing out faster than if the tire were correctly inflated. But with gas prices where they are, it still may be an economic win. Traction is less though, so there is an increased chance of crashing in some situations.

[Loren Booda]

Very interesting.

I don't think that my tires are so overinflated, though. Assuming the tires are now at the correct pressure, do my figures above agree with automotive experience?

[Integral]

I increased my tire pressure by 2psi and saw about a 2mpg improvement in gas mileage. Sounds similar to what you are seeing.