Stop-start setup can save gas in long run

• System turns engine off when vehicle stopped%2C restarts it when a driver presses the accelerator
• 50 percent of new cars in Europe offer the technology
• Chrysler plans to deploy technology to most of its fleet by 2017

DETROIT -- Stop-start technology can improve the fuel economy of a car or truck by 15%, but the jury is out on whether consumers are comfortable enough with their engines shutting down and restarting automatically.

The systems save on fuel consumption because they turn the engine off when a driver comes to a stop and restart it when a driver presses the accelerator.

In Europe, about 50% of the new cars offered by automakers come with the technology, either as a standard feature or an option. In the U.S., only a handful of models offer the system, which can cost several hundred dollars.

"We all can put good systems into production," said Scott Dahl, regional president of Robert Bosch's motor division. "But what we need to do is make sure the consumer is informed. We need to let them know what is happening in the vehicle."

Dahl and others who spoke Tuesday at the SAE 2013 World Congress in Detroit said U.S. consumers are still apprehensive about allowing their engines to be turned off at a stoplight.

There are other possible problems. On a hot day, drivers don't want their air-conditioning to be turned off.

Some consumers don't like the engine noise that comes with restarting the car.

But Robert Martin, director of supplier Denso's engine group, argues that the industry sometimes worries too much about how sensitive consumers are.

With a good start-stop system, many consumers don't even notice that the engine is on and off.

Martin said the benefits are greater than any initial discomfort.

"If a car is idling, it is wasting fuel," Martin said. "Most people probably don't have a good handle on how much idling they actually do."

Michel Forissier, development director for Valeo powertrain systems, said start-stop systems typically cost $400 to $500.

Forissier estimates that drivers can recoup that investment in one to three years, depending on the kind of driving they do. People who drive in congested cities get a greater benefit than those in rural areas.

Europeans were slow to embrace the technology, Forissier said. Manufacturers pushed ahead because it helped them meet stricter fuel-efficiency standards.

Now, the U.S. automotive industry is racing to meet new standards that will be nearly as strict by 2025.

Mark Rakoski, executive director of Mitsubishi Electric Automotive America, said he expects 8 million cars and trucks in the U.S. will be sold with start-stop systems by 2020.

Chrysler, in its annual report in 2012, said it plans to deploy start-stop technology across 90% of its fleet by 2017. It offers a Fiat-developed system as an option on its Ram 1500 pickup.