— Engineers have made cars more aerodynamic. Also, some vehicles shut off their engines automatically at stoplights. They can run pumps and other devices off the battery rather than a belt that sucks power from the engine.
Even as they become more powerful, smaller engines are helping lower gas consumption. So far this year, consumption is down 5 percent from the same period a year ago, according to government data.
Part of the drop is because people drive fewer miles in a weak economy. But engines play a key role. The average new car goes about four miles farther on a gallon than in October 2007, said Michael Sivak, a research professor at the University of Michigan Transportation Research Institute.
In March, the average mileage of new cars hit a record 24.1 mpg, dropping slightly since then.
The improvements become more striking when drivers compare engines. Four-cylinder engines averaged 26.4 mpg this model year, compared with an average of 16.1 mpg for eight-cylinders, Sivak said. If gas were at $4, the average driver would save roughly $1,300 a year by switching to a car with the smaller engine.
Hyundai was so confident in its four that it stopped offering a V-6 in the 2011 Sonata. Chevrolet and Ford are doing the same on the new Malibu and Fusion, which go on sale later this year.
In fact, eight out of 10 midsize cars sold this year had four-cylinder engines, according to the Edmunds.com automotive website. Just a decade ago, the majority of midsize cars — normally the biggest segment of the market — had V-6 engines.
In the heyday of the muscle car, automakers tried to stuff the biggest engine they could into smaller cars. Now it's the opposite. Companies are putting smaller engines in larger vehicles, even in Ford's F-Series pickup truck, the nation's top-selling vehicle.
In 2011, Ford began offering V-6s, including a turbocharged engine, in the F-150 after years of selling only V-8s. Now nearly 60 percent of F-150s are sold with V-6s, and Ford expects that to increase. The V-6 turbo gets 18 mpg in combined city-highway driving. The V-8 gets 14.
It didn't take long for Colorado real estate agent Dan Murphy to switch to a smaller truck engine.
A year ago, he bought a Ram pickup with a V-8, only to find that the mileage was awful when towing his 19-foot boat through the mountains. The Ram, he said, got only 4 mpg at one point, costing him a fortune.
So he traded it for an F-150 with a turbo V-6. On a recent trip pulling the boat to Utah, his Ford got over 17 mpg.
"Once you drive this, there's no way you're going back to a V-8," he said.
At Fiat of South Atlanta, the trend toward smaller engines is driving up sales of the 500 mini-car, which until February had been selling slowly.
"We've had several people trade in Ford Tauruses, not a bad mileage car," said sales manager James Tharp. "People will say in a heartbeat, 'These gas prices are killing us.'"
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