Gas Mileage

[MaineBimmerKidd]

Hi, I'm somewhat new to the tuning arena. I guess one of my questions, it may be obvious to some, is how much is gas mileage affected with larger wheels? Currently I have a 318i, with the 15" stock alloys, and I'm getting anywhere between 26-30 MPG. I was looking to get some 17" rims but I guess I'm concerned with fuel economy. Any input?

[lovesm3s]

if they are lightweight the difference isn't too much. i run 15's that weigh 40lbs with my tires (205's all around) on them and i get about 400 miles per tank and with my 17's that weigh 40 with tires (245's all around) as well i get about 370 to 380. That's mostly highway miles.

[Daved]

I don't think they make a big difference.

I went from the stock 15"s to some heavy 18"s and I don't remember that I noticed any difference in the gas mileage.

[BMWdisease]

"Grassroots Motorsports" did a study on heavy wheels a few months ago.
Oversimplified: They said a wheel/tire combination that is 5 lbs heavier than stock, because of additional energy to get it moving, or stop it, equates to an additional 20 lbs. (weight of wheel times 4, (roughly)). Multiply that by 4, for each wheel, and it would be like carrying an extra 80lbs in your car.

So maybe you're on the gas ever so slightly more to get you moving, but no biggie.