Everything You Need to Know About Tires and Gas Mileage

Once you've got the basics of fuel economy down, it's time to start getting a little more involved. And what's a better place to start than with talking about tires?

There is very little that's more universal about cars than tires -- every car has them, and almost every owner has gone through the experience of having to buy new ones when the old ones meet their fate.

However, what most people don't know about tires is that they have a huge impact on fuel economy. When you're browsing reviews online or at a store looking at tires, no one jumps out to tell you about rolling resistance or how tire sizing affects overall gearing, so these bits of information tend to go unnoticed.

Recently there has been a lot of talk about keeping your tires pumped up to manufacturer's specs, with some motivated souls going as far as to calculate possible fuel wasted if everyone was driving around on underinflated tires. There is a bit more to tire inflation than meets the eye, though.

The recommended inflation you will find in the vehicle's owner manual (usually 32-35 psi) is based on a number of factors, including traction, comfort, and fuel economy. On the sidewall of the tire, you will find another number (usually 44 psi or 51 psi), which is the maximum pressure the tire is designed to hold safely. Knowing that higher pressures reduce rolling resistance, therefore increasing fuel economy, many enthusiastic EcoModders (myself included) have filled their tires up to the maximum listed on the sidewall.

Does it work? Yes, there is a bump on the order of a percent or two difference between low and maximum tire pressures, but the real question is what of those other considerations put together by auto manufacturers who recommend lower pressures? Well, it seems those lower pressures are mainly for comfort, not safety. Officer.com, a site for law enforcement, addresses the issue of tire inflation directly:

If you look on the sidewall of the tire, you will see that it lists 44 psi max pressure. Regardless of what vehicle you have, use the maximum pressure listed on the sidewall. Higher pressure results in better performance, decreased tire wear, and it lessens your chance of hydroplaning at a given speed.

That said, you still need to be careful when pumping up your tires to the max. You may notice a slightly rougher ride, and as with any change in your tire pressure, your car will handle a bit differently. Make sure nothing gets funky, because safety is much more valuable than gas. At the very least, make sure you check your tire pressure often and keep it at the level of your choosing. Also check with warm tires, as the pressure changes when you get out on the open road and your tires heat up.

Now, tire pressure isn't the only way to lower rolling resistance. Low rolling resistance (LRR) tires have been getting a lot of press recently as a possible way to increase fuel efficiency in an easy way. These tires have been on cars like the hybrid Honda Insight and Toyota Prius since they have come out, but they're also available to consumers, although the information can be hard to come by. Next time you need tires, make sure to research the latest on LRRs to see if there are any available for your car.

Tires are so simple that they're easy to forget about, but part of that simplicity is what makes it so easy to gain a few MPG from them. Just paying attention to your tire pressure or making the LRR decision next time you need to will make a difference, so don't forget!