By 2025, new cars and trucks sold in the U.S. will have to average 54.5 miles per gallon of gasoline, up from the current 30.8 mpg. One feature will almost be a must-have: A ‘‘stop-start’’ device that shuts off the engine at a stop light and automatically turns it on when the driver releases the brake.
Alex Molinaroli, a vice president with Johnson Controls Inc., which makes batteries that power the systems, estimates they raise gas mileage by a minimum of 5 percent.
Stop-start first surfaced in Europe, where gas prices are far higher. Now, nearly all gas-electric hybrid vehicles have it, as do some cars and trucks with conventional engines. The BMW 3-Series has a simple system, helping the four-cylinder version with an automatic transmission get 28 mpg in combined city and highway driving. A high-mileage version of Chrysler’s Ram pickup also has it, boosting combined mileage by 1 mpg to 21.
Currently, 5 percent of new U.S. cars have the systems as standard or optional equipment, up from just 0.5 percent two years ago, according to the Edmunds.com automotive website. Johnson Controls predicts that to rise to 40 to 45 percent by 2016.