How do tires effect gas mileage?

Host: How do tires effect the gas mileage?

David Rizzo: Significantly, tires have a big effect, in fact 20% of the energy to move your car down the road is overcoming the rolling resistance of tires. So 20 % is a lot, you want to keep your tires inflated and I would go by the manufacturer's recommendation, again check in your car manual. However, let's say your first set of tires were out, you have got new tires on there. They are not the same as the original or you buy a used car, then I would go by what's on the sidewall of the tire and it will tell you, the average is about 35 pounds of pressure per square inch. You never want to have the tire under-inflated, never, because for every pound under inflation you loose 2% miles per gallon. So if you are running long and tires are at 25 pounds of pressure and it should be 35, that's 10 pounds below, that's 20% decrease in miles per gallon. Huge gains can be gained just by putting enough air in your tires. You also want to resist the temptation to pimp your ride. I know a lot of people want big rims, low profile tires, it's the worst thing on your gas mileage. Low profile tires have higher rolling resistance, the big rims weigh more and like I said for every 50 pounds of extra weight you loose 1% of gas mileage.

If you are in a dry climate, don't wear rain tires, you don't need rain tires in a dry climate and rain tires have more rolling resistance. Also if you are in a pickup track and you are hardly ever going to dirt, don't go for really aggressive off-road tires. Again off-road tires have greater rolling resistance, it cuts down on your gas mileage.