Quote Originally Posted by bangbangskeetskeet View Post
Rotating mass creates a bunch more load than you would expect. So a few extra pounds on each corner adds up and is a significant difference.
Going from 16s to 17s "SHOULDN'T" cause 4 mpg difference though. Depending on the wheels, you're talking about 25 pounds added at the MOST. Then bigger tires, maybe 50 pounds total. Not like the 200 pounds I increased.