Regardless of whether you drive a car or a truck, your tires affect how much mileage you get from your gas tank. Depending on their composition and tread design, among other factors, some tires are better for your vehicle's fuel efficiency than others. Tire rolling resistance, or the forces that counteract a tire's rolling movement, can impact a car's fuel economy by as much as 15 percent, and even higher for trucks. While a very small amount of rolling resistance comes from internal wheel friction, the majority of tire rolling resistance is caused by hysteresis, a natural property of tire rubber and other elastic materials.
A driver burns a certain amount of fuel to supply the wheels and tires with the energy to overcome inertia and move the vehicle. Due to the vehicle's weight pressing the tire against the road, the tire's shape is slightly flattened at its contact patch, causing the rubber to deform (flatten) and rebound (become round again) as it rolls. Since it takes more energy to deform than to rebound, this continuous flexing absorbs some of the tire's kinetic energy, causing it to lose momentum over time. This effect, called hysteresis, requires the driver to burn additional fuel and supply more energy to keep the tire rolling at the intended speed. The more a tire flexes, the more kinetic energy it loses to hysteresis, and the more fuel the driver needs to burn to travel a given distance.
Proper air inflation is key to reducing tire deformation, tire hysteresis, and rolling resistance. Higher air pressure helps to maintain a tire's roundness, reducing how much its shape deforms and rebounds while rolling. The more a tire is inflated, the less less kinetic energy it loses to hysteresis, so a fully inflated tire has less rolling resistance and more fuel efficiency than an underinflated one. That said, since an overinflated tire is less flexible, it is also more sensitive to road imperfections, resulting in a less comfortable ride. Additionally, because the tire puts less rubber in contact with the road, it is less capable of providing traction.
Tire rolling resistance is affected by several other factors as well. Due to increased rubber mass, a heavy-duty tire needs more initial energy to overcome inertia and puts more weight on the contact patch, so a 6-ply truck tire generally has higher rolling resistance and lower fuel efficiency than a standard passenger tire. Additionally, tires with deep tread depths and wide tread voids flex more easily and generate more internal friction, so a mud-terrain tire has increased rolling resistance and decreased fuel efficiency compared to a highway-terrain tire. For similar reasons, new tires initiallly have more rolling resistance than the tires they replace, though the safety hazards of using worn-out tires far outweigh the benefits.
Some tires today are specially engineered for low rolling resistance. Often called fuel-economy tires or Low Rolling Resistance (LRR) tires, they typically feature special tread compounds and reinforced sidewalls to help to reduce tire deformation and more retain kinetic energy while rolling. In the past, decreasing a tire's rolling resistance also decreased its ability to provide road grip. However, many tires today are engineered with silica-containing rubber compounds, which decrease rolling resistance without sacrificing traction capabilities. Since low rolling resistance tires don't lose as much kinetic energy to hysteresis, they maintain their momentum longer, letting your vehicle to get more mileage out of every gallon of gas.
On average, a set of low rolling resistance tires improve your vehicle's fuel economy by about 3 percent overall. While this may seem like a trivial difference, this boost to fuel efficiency can save substantially on gasoline spending costs each year. For instance, if the average driver spends about $2,000 on gasoline annually, then 3 percent cost savings comes out to about $60 per year. The cumulative cost savings from low rolling resistance tires can add up considerably over the tire's 3 to 4 year lifespan, and can even help to offset the cost of your next tires.