Originally Posted by Soccerluvr4
Also have to take into account how at highway speeds larger wheels will make the engine turn less rpms. So if you can find the balance between weight and size you can get better mpg.
A 275/50r15, 275/35r18, 225/30r20 are all going to rotate nearly the exact same. Within .5 mph difference at 65.
---------- Post added at 05:21 PM ---------- Previous post was at 05:16 PM ----------
For the op.
These tires are within .01 inches of each other.
The 20" will get worse mileage than the 19" and the 19" will get worse than the 18".
With this model I am making the assumption that the wheels are made of identical material in an identical pattern.