don't know how but i just put 35s on. my 22re has at least 220k and i'm at 20mpg...but i can only do 40-45 up the canyon i have to drive to work. everybody is passing me at 70. just ordered my 5.29s for some power and so i don't wear on the clutch so much.
btw i used to get 21mpg with my 31s,
this is with 4.10 gears