Flat tire, by Flickr user Lissalou66
It wasn't always this way. In the past, using low rolling resistance tires meant that you'd get slightly higher mileage, at the expense of many more noise, limited tread wear, and greatly compromised traction and grip in the wet.
But Consumer Reports, in its new July issue now hitting newsstands, tested low-rolling-resistance tires and confirmed that they offer much better performance than they used to—with all-around ratings for three-season use as good as those for many general all-weather tires.
Rolling resistance, which is due mostly to the flexing of tire sidewalls and the gripping action of the tread, accounts for about four percent of fuel use in the city and about seven percent on the highway, according to the U.S. Department of Transportation.
What makes the new ones different? In the past, says CR's tire program leader, Gene Petersen, rolling resistance was cut—literally—by shaving weight off the tire and using a slightly different, tread design that was also much shallower. "Unfortunately, when you develop a tire along those lines, tread life and wet grip are compromised," he said.
Better compounds make it possible
Petersen says that in newer tires, much of the improvement is in the compound; adding silica to the compound, in place of carbon black, is a start.
In the latest tests, the Michelin Energy Saver A/S had the lowest rolling resistance of any all-season tire evaluated by CR in recent years, yet it also earned "good" ratings for snow traction and ice braking and performed well in hydroplaning resistance and emergency handling. And with as long of an estimated tread life as most all-season radials, it's truly a greener choice.
Petersen says that the Goodyear Assurance Fuel Max and Cooper GFE are also among those that should rack up fuel-cost savings without compromising performance. The Cooper GFE was a surprisingly good tire for winter grip as well.
Green tires no longer just for green cars
The other change is that 'green' low-rolling-resistance tires are being delivered for the replacement market; they aren't only offered in just a few sizes that are intended only for hybrid or diesel models. "We're seeing them sized for most family vehicles today," he said. Before, they'd only been designed for specific original-equipment applications, where they helped to achieve slightly higher EPA ratings while sacrificing performance in some way.
Petersen says that out of 69 tires the organization tested last year, the Goodyear Assurance had the lowest rolling resistance. CR found that on a four-cylinder Chevrolet Malibu, versus the tire choice with the highest rolling resistance, an owner could save 3.1 mpg—that's over $100 per year. Most people who upgrade to low-rolling-resistance tires from the average vehicle tire are going to see about half that, said Petersen—still enough to save some money in the long run.
But you shouldn't buy a tire only for its potential to save fuel, cautions Petersen, or you might be disappointed. Since a new tire with deep tread is always going to have more rolling resistance than a worn, almost-bald one, if you're the type to hover over your trip computer you'll see only a slight difference at first. CR advises that you choose a tire that's right for your road conditions and driving season, then use rolling resistance as a tie-breaker.
Of course, the same advice that applies to other types of tires applies to these. That means you have to maintain the inflation pressure and manually check it monthly. Proper vehicle maintenance—including proper alignment and replacing worn suspension pieces—is also a must, and to get the most out of them you should be careful in how you load a vehicle.
proposed federal tire efficiency label
Federal tire ratings coming soon
This March, the federal government proposed a tire rating system that would gauge tires on three attributes: Fuel Efficiency, tread life (Durability), and wet traction (Safety). The rating system might result in a new sidewall label, and perhaps a certificate that explains the attributes at the time of purchase.
The state of California has also been working on a system of rating tires for fuel efficiency, and make it mandatory for manufacturers to supply rolling-resistance information. The top 15 percent of models would have been awarded with something similar to an Energy Star rating.