The key to your statement is "if all else is equal". Unfortunately, it never is. In reality, larger wheels are usually heavier, so your gas mileage will decrease slightly. Also, if your new wheels and tires are wider, there will be more wind resistance, which will also lower gas mileage. But the difference we are talking here is rather minimal. Maybe 10% difference at most, unless you are putting monster tire sized wheels on your truck.

I lost about 1 - 1.5 mpg when going from 17s to my current 20s. I figured it is bc of the added weight of the new wheels.

Right. I guess unless you found some lightweight racing wheels that were also the same width as the stock rims, then you are probably going to lose MPG's due to the added weight and increased contact patch.

I guess the manufacturer probably takes all of that into consideration when deciding what size wheels to put standard on the car to begin with.

Yes. And while most of us on car message boards are more interested in performance, the majority of consumers are more interested in gas mileage and ride quality, so the manufacturers usually put smaller and narrower wheels on cars as standard, and then offer upgrades in their "sport" package.

I've Installed 22inch Nitros and notice absolutely no difference in mileage. Personally, "nuff" said.

You would have to be analyzing the hell out of your driving style and MPG's before and after to notice the difference. It wouldn't be very noticeable otherwise. The difference would be fairly small anyway. There are too many variables also to just base an answer off of what you have personally observed such as tire pressures, driving style, actual roads driven on, routes taken, ambient temperatures and so on.

I bet you probably haven't noticed increased stopping distances either, but if you were to test it with the stock rims and then again with your oversized rims in a controlled environment there would be a small difference.

Exto Mundo.............if we are getting down to that degree....it's a bit too annual retentive 4 me. I've got other irons in the fire. LOL

I agree. It would typically be a small amount and could probably be considered insignificant by most as far as MPG's go. Not trying to split hairs.

Your 22's affect the performance and ride of your X more than MPG's.

Wheel Tech - Road Wheel Weights Can Affect Your Vehicle's Show...and Go

Best MPG is achieved with 3 tires..less rolling friction

That would explain the 150mpg Aptera.

http://apgaylard.files.wordpress.com/2008/09/aptera.jpg