What is auto stop/start? Autoweek explains

Fuel-saving stop/start tech is showing up everywhere; here's how it works

If you've shopped for a new car in the past few years, you've probably seen automakers touting new stop/start systems that can help save a little gas money. The concept is simple enough -- if you're stopped at a red light or train crossing, you don't need the engine; if the engine isn't running, you're not wasting any energy. But what's really going on?

As the name implies, automatic stop/start shuts off the engine instead of it idling at a stop and then rapidly restarts the engine when you want to drive away. If you do a lot of stop-and-go driving, you're reducing emissions and saving fuel by not idling for extended periods. More important to the automakers, adding stop/start tech increases Corporate Average Fuel Economy (CAFE) figures, helping offset all those big SUVs being sold.

Automatic stop/start systems do present engineering challenges. The electric starter that was designed to fire your engine a few times a day now has to start the same engine every time the car comes to a full stop. Obviously, a starter that was designed for 50,000 start cycles can't suddenly be responsible for 500K start cycles, so automakers have phased in special starters to better handle the stress.

The frequent cycling can strain internal engine parts, too. Most engine wear and tear happens during startup, so engineers have designed bearings that better self-lubricate and are slicker than normal bearings. Better self-lubrication means the engine will be better protected until pressurized oil arrives after the engine is running. Even without special bearings, engine oil technology has also improved, meaning there's a better layer of protection already on the bearings to prevent excessive wear.

With automatic stop/start and an automatic transmission, holding the brake after coming to a complete stop will usually trigger the system to shut down the engine. Lifting your foot off the brake (and, on some systems, turning the steering wheel) will restart the engine, usually bringing it up to speed by the time your foot reaches the accelerator pedal. With a manual transmission, shifting to neutral and releasing the clutch generally switches off the engine; pushing in the clutch pedal starts it back up, and the car is ready to go by the time you have it in gear. Depending on the vehicle, the engine may also restart if the climate control system needs additional heating or cooling; the system may also deactivate if the weather outside is above or below a certain temperature.
Will this save you thousands of dollars in gas? Not likely, but if you live in a congested area, the few extra miles you might get from a tank of fuel will add up, as will the less-visible emissions benefits. More importantly, you shouldn't have to worry about added stress on your car -- it's been engineered to deal with the new technology.

h/t Autocar

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