Hello, just bought a 07 tahoe LTZ 4x4. It has aftermarket chrome 22' rims on it. Was just curious how much rims like these affect gas mileage? I have been tossing around the idea of trading someone for the factory 20' gm rims instead. I'm getting about 14 mpg half city half highway and that doesn't seem like a whole lot??? Any input would help. Thanks