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How Tire Choice Affects Gas Mileage

Posted in How To: Wheels Tires on March 1, 2012
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Much like a fat guy in a speedo, there are just some things that jump out at you and are impossible miss. Unfortunately, many of the things that go awry with our Jeeps are not so obvious. Our past story (“Gaining Through Losing,” Oct. ’11) got us thinking about it. Not the fat guy in the speedo, but the impact that tire selection has on mileage. In that story we picked up 0.63 mpg by simply losing 28 lbs of rotating weight at each corner, or 112 lbs of total rotating weight lost. But what about the tread design? Despite using two different brands of tires, we kept the tread design as similar as possible for that test. As we kicked the idea around more and more, we decided we likely had enough data from enough different vehicles to figure out just how different tires affect mileage.

Now we aren’t saying all the changes we’ve recorded below are from tire weight. Maybe they are from the aggressiveness of the tread, but how much? We all know that going to a bigger tire with the same gears kills mileage, but how much? Or does it? The fact of the matter was we just weren’t sure anymore. But, fortunately, we keep tons of records, including when we swapped tires and how many miles were driven on a given tank for just about every vehicle we own. So, we broke out the calculators and notebooks and set about figuring just how a particular set of tires changed our mileage.

Some of our measurements were obviously with different-sized tires, but some, such as these two 285/75R16s are just about as apples-to-apples as you can get. They are the same height, tread width, and are within a few pounds of each other, mounted on their respective aluminum rims. In this case, the 1⁄2 mpg difference is most likely because the Cooper tire (left) has a more aggressive tread pattern than the Goodyear tire (right).

The Guinea Pigs
Our cast of characters is long and convoluted. We even included Editor Hazel’s tow rigs over thousands of miles.

We threw away mileage data where we went wheeling since every wheeling trip is different. We only used good ol’ boring street mileage to calculate our numbers. So our mileage numbers are an average taken over thousands of miles driven both in town and on the freeway. And, we even were careful to throw away the mileage numbers where we were stuck in wonderful SoCal traffic.
tires Milage And You tires And Mileage Chart Photo 34937645

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