As I drove the new, redesigned 2012 BMW 335, I came to the place where I needed to make a left turn on a Monterey, CA road. I stopped the sport sedan to wait for oncoming traffic to pass. The engine cut out with a gentle rumble.

A problem? Out of gas? No. It was just the stop-start system kicking in, shutting down the engine and thus gas consumption. When traffic cleared, I stepped on the gas pedal, and the BMW responded immediately with perhaps just a hair of a delay, compared with a Bimmer without the system.

BMW has made the system standard in the new 3, and it will become standard on all BMWs just as it is becoming standard on an increasing number of new models.

The new 2012 Chevy Malibu ECO also sports stop-start. The system works a bit differently than BMW's. I had to strain at stop-lights and left-turn stops to even know that the engine was off. The transition from revving to stop and then to start was so invisible and quiet that I had to double check that the Malibu ECO actually had the system on-board.

The electric motor automatic stop-start system on-board the Malibu ECO, and other vehicles with a similar system, also cuts fuel to the engine entirely upon deceleration for more gas savings.

The technology has been wide spread in gas-electric hybrids but has now moved over to conventional vehicles to improve mileage and lower emissions by shutting off the engine when it's not being used. Instead, the car's systems, such as stereo, heater or air conditioner, gauges, lights and windshield wipers run directly from the battery, while the engine is off.

For some traditionalists, the system will be disconcerting. "There is no question that there are drivers and car buyers who are going to have to be walked through it--how it works and why it is on their car," says Rebecca Lindland, chief of auto industry analysis at IHS Global Insight. Indeed, Chevy and Kia dealers, to name two, have been put through extra training to make test-drives with prospective customers go smoothly for people to whom the technology is brand new.

Indeed, not all stop-start systems are alike. Kia Motors intended to put the system in its 2012 Kia Rio and Kia Soul, but has delayed equipping those cars with the fuel saving tech because journalists reviewing the vehicles criticized Kia's systems for being too rough when shutting down and re-starting. BMW is receiving criticism as well.

Over the next ten to fifteen years, the vast majority of new cars and trucks will adopt the system.

Johnson Controls, a leading supplier of the systems to automakers, says that the number of vehicles equipped with stop-start technology will at least triple within the next five years. Globally, Johnson Controls figures, stop-start tech will be standard in 52 to 55 percent of vehicles built in 2016, up from eight percent in 2010. The automotive supplier forecasts that nearly 25 million vehicles built in 2016 will come with an idle-stop system, up from seven million vehicles in 2011.

How much fuel does it save? Shutting down the engine while idling can reduce fuel consumption and emissions by up to 12 percent in conventional gasoline-powered vehicles. Secondly, in the drive to improve fuel efficiency, stop-start technology has an edge in costs over some of the more advanced fuel-saving systems. It's estimated that idle-stop costs an automaker no more than $1,500 to install, versus $5,900 for an advanced "clean" diesel engine and $6,000 for a full hybrid system.

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