Lower MPG with bigger wheels?

[SteelBlueGT]

Yes, everything being equal (never is in reality) the more contact area hitting the road; the more drag or friction; the worse gas mileage!!

[eliminator]

quote:Originally posted by Gunner

Has anyone experienced a lower miles per gallon after installing a larger diameter wheel? I am trying to find out if this is normal, or if something else is wrong with my car. I'll try to post some pics of my baby's new shoes next week after I get my digital camera. Yep, Christmas came a little early this year!!

Are your new tires the same height (or circumference) as the original ones? If the tires are taller, you're gearing the car higher and slowing down the engine and odometer. The odometer will show fewer miles than what you actually drove, and your milage will be worse on paper than in reality. The opposite will be true if the new tires are SHORTER than OEM.

And then there are the other things mentioned above like wheel/tire width and weight. There's a reason that economy cars have skinny, tall tires. It really does make a difference.

[Gunner]

Well here is a quick little update on the wheel and tire problem. I changed back to factory set this weekend and did some driving. My MPG increased by 4 1/2 MPG. The aftermarket wheels and tires are 18 X 7.5 with 225/40 18's. I am going to leave them off for winter, or maybe even longer with the big reduction in gas milage. I guess looking good comes at a price. [:0]

[eliminator]

225/40-18's are exactly the same height as the 205/50-17's that are stock on a GT. If those are the tire sizes you're using, the difference in milage is apparently entirely due to weight and tire width.

I wonder if installing the (presumably lighter) base model wheels in place of the GT's 17's would improve gas milage?