I used to average around 20-21 mpg. About 3 weeks ago, I replaced the OEM 18" wheels with 19" Volks. Since then I've been averaging appx. 18 mpg. Does adding bigger wheels effect the mileage that much?

Added weight / larger overall diameter will effect gas milage.

On my Jeep I went from 20 mpg to 12 mpg when I put larger tires on it. Not that we can our diameter can change that much, but that is my experience.

More rotational mass + Weight = more rotations = more work for the engine

the volks didnt feel that much heavier than the 18s

Are the 19" (presumably wider) tires heavier? That's were the weight really matters, not 1 or 2 lbs on the rim....

i meant the OEM 18s with tires compared to the volks with tires

def bc of the tires

The Torque required to rotate the tires is based on radius, so weight farther out takes more to rotate than the same weight closer in.

gotcha, thanks

Is the diameter of your 19" tire on the wheel, tread edge to tread edge, larger than the 18" (you could measure circimference also)? If so, your odometer could be reading slightly less than actual miles. I computed mine at about 2-3% larger, which means that 100 actual miles registers on the odometer as 97-98 miles.

im running 245/35 in the front and 275/35 in the rear and they do look slightly larger in diameter than the OEM tires