Tires: tires, mileage calculation, s10 blazer

Question
i went from a 205 75/r15 to a 215 70/r15 on my s10 blazer. should that affect my gas mileage? the tire dealer told me it was basically the same tire.

thanks

Answer
Mike,

The tire is a different size, so it is physically wider and a little smaller in diameter, but that shouldn't have affected the fuel economy, except to say your speedometer is now reading 1% low, and that might affect you mileage calculation a little in the wrong direction.

But what likely happened is that new tires have higher rolling resistance than worn out tires - every thing else being the same.

Plus, changing from OE tires to replacement market tires can also adversely affect fuel economy.  I explain all this in more detail here:

http://www.barrystiretech.com/rrandfe.html