Where the Rubber Hits Your MPG
Whiz-bang car technology allows hybrids to get 50 mpg, and electric cars to earn the equivalent of 100 miles per gallon. But you don’t have to go high-tech to improve your fuel efficiency. Significant gains in mpg are available to anybody paying attention to their tires, no matter what vehicle you drive.
“Choosing the right tire can have a big impact on fuel efficiency, just as choosing the vehicle makes a big difference,” said Woody Rogers, product information specialist, at Tirerack.com. Rogers and his colleagues at Tirerack.com repeatedly test the efficiency of tires. “In our testing of hybrids, we’ve seen a 5 mpg gain—a 10 percent swing from a best to worst scenario,” he said.
One critical factor is rolling resistance. The U.S. Department of Energy’s Alternative Fuel Data Center defines rolling resistance as “fundamentally the parasitic energy a tire consumes while rolling under load.” The D.O.E. says this phenomenon is complex, with any number of driving conditions affecting the outcome on fuel efficiency. Regardless, the D.O.E. estimates that 5 to 15 percent of light-duty fuel consumption is used to overcome rolling resistance for passenger cars. That number jumps to 15 to 30 percent for heavy trucks.
So, what tire makes the most sense for fuel-conscious consumers? You could start with the tires that carmakers choose to put on fuel-efficient cars in the factory. The Goodyear Assurance Fuel Max is the high-mpg weapon of choice for both the Toyota Prius and the Chevrolet Volt. “Today, pretty much every tire that comes as an original equipment tire on any vehicle is tuned for that vehicle,” said Rogers. “It’s tuned for what the vehicle engineers have asked for, in rolling resistance, traction, handling, ride quality, and noise level.” Nissan chose the Bridgesone Ecopia EP422 for the all-electric Nissan Leaf.
Tirerack’s Rogers adds the Michelin Energy Saver AF to his short list of green tires. “That tire proved to work best with the testing we did on the Toyota Prius last year, and considering Michelin’s excellent reputation for rolling resistance and tread wear.” He also suggested a couple of summer-only tires—the Yokohama dB Super E-Spec and the Bridgestone Ecopia EP100.
There are some compromises with buying low rolling resistance (LRR) tires, including faster tread wear and some loss of traction on wet roads. Each tire has to be evaluated for those factors.
ROI on LRR
Then there is cost. Rogers believes that effective low rolling resistance prices will become cost-competitive—like any innovative technology that becomes more affordable over time. “We’re probably still years away from the most efficient tires being very inexpensive,” he said.
Even at today’s prices, the California Energy Commission (CEC) issued a report indicating that the fuel savings over time pays for the slightly higher upfront cost of low rolling resistance tires. And if every Californian switched to low rolling resistance tires, the state’s motorists would collectively save 300 million gallons of gasoline every year.
Anybody can save that 3 percent right away, simply by keeping tires properly inflated, according to FuelEconomy.gov. And pumping in more air costs nothing—or next to nothing. “Maintaining the suggested level of air pressure can have a bigger influence on fuel efficiency than choosing an ultra low rolling resistance tire,” said Tirerack.com’s Rogers. The simple rule of thumb is to check tire pressure once a month. “Checking too often is definitely better than less often, or not at all as many consumers do.”
For more information about fuel efficiency, visit eBay’s Green Driving Center.