Most of us who grew up driving four-cylinder, carbureted economy cars are familiar with start-stop technology. Thirty years ago, it wasn’t a selling point, but rather the byproduct of carbureted engines attempting to meet ever-stricter emission requirements. The result was a car likely to stall under even moderate loads (the air conditioning compressor, for example) at traffic lights. If you lived at elevations above sea level, the problem got worse. Back then, we cursed cars that stalled at traffic signals--and had to coax them back to life before the light turned green. And they arguably might have been saving a little fuel (but probably not).
Today, start-stop is a legitimate feature that both certainly does save gas and reduces tailpipe emissions.
In 2010, only eight percent of new cars (such as Toyota's Prius, or Ford's Fusion Hybrid) had start-stop technology, which shuts down the engine when the vehicles comes to a rest for more than a few seconds. Depressing the accelerator will instantly restart the car, and systems such as climate control, headlights and audio remain operational while the engine is turned off. The whole thing is almost seamless to drivers, who may not even notice that their car’s engine has stopped running. The feature can reduce fuel consumption and greenhouse gas emissions by as much as 12 percent, depending upon how much time is spent in city driving.
Johnson Controls, a leading supplier of start-stop system components, estimates that up to 55 percent of new cars will employ this technology by 2016. That’s a global number, but the percentage is even higher for the European market, where 70 percent of new vehicles sold in 2015 are expected to be fitted with start stop systems.