The mpg difference between 17" and 15" tires

[kev]

Originally Posted by capnbass91

I tested the accuracy of the odometer by seeing if 1 mile on my odometer was equal to 1 mile maker on the highway, and it was accurate. Did this on a long trip and didn't get off one bit. Also doubled checked the distance on google maps, the trip length matched what I had on my trip odometer. It was also calibrated when I got my knew tires, and so far it's right on still.

I have my old tires, and when I put them next to my new ones the 17"ers are definitely bigger.

If the odo wasn't calibrated for the old tires, then it would have been giving you falsely-lower MPG calculations. Then, putting stock tires back would bring the numbers back to where they should be.

[eldiee]

When the Gen 3 Prius was introduced in 2009 the difference between the 15" and 17" in wheels on their(Toyota) tests for EPA was 3 mpg. Part of the difference was due to heavy wheels for the 17" size. I think the tires and wheels for 17" were almost 4 pounds over the 15" size. That would take more energy to start moving each time causing a drop in mpg. I have a 2010Prius V with 17" wheels and was willing to give up the 3 mpg for the way the car handles compared to the other Prius models with 15" wheels.That being said, I still have a lifetime average of 55mpg on the cars computer. However that is about 3 mpg higher than measured. I still am quite satisfied with our model V(5) 2010 Prius.

[Frank Lee]

I've read that it takes 4000 miles for new tires to break in i.e. expect higher r.r. until then.

[mcrews]

I really dont understand how we get to the second page with a factual discussion about diameter of the actual tire??
the assumption that the tires are the same diameter is weak at best.
Also the wieght of the each size of tire and the weight of the rims.
the poster was correct that once you are rolling, a little extra wieght is not going to matter.