Does stop-start technology wear engines down?

If you live anywhere near a city and drive a vehicle, you know that a large percentage of your time behind the wheel is spent waiting: waiting at stop signs, waiting for traffic lights to change colors and waiting in bumper-to-bumper traffic.

One consequence of all that waiting around is wasted fuel. After all, any fuel that's burned while you're not moving is literally wasted energy. But stop-start technology slams the brakes, so to speak, on idle combustion -- by shutting off the vehicle's engine when it comes to a stop. When the driver gets ready to move forward again, by pressing the accelerator or pressing the clutch, an electrical generator in the car quickly spools the engine back up (within milliseconds) so the vehicle can drive away.

We've seen this used to great effect already in many hybrid gasoline-electric vehicles, including "mild hybrids" such as the discontinued Chevy Malibu Hybrid and Saturn VUE Green Line Hybrid. But start-stop technology also works on non-hybrids. It's already popular in Europe, and the equipment is expected to soon become normal in the United States, as automakers rush to deploy every feasible technology to comply with toughening fuel efficiency standards. Estimates vary, but depending on the application, start-stop could make a vehicle up to 15 percent more fuel efficient.

But weren't we told at some point that it's not good to stop-start, stop-start your engine? Isn't that supposed to place undue wear and tear on the engine? Well, let's think about that one. When engines wear, what's usually meant is that oil is not adequately bathing and lubricating the metal-to-metal contact points throughout the engine. Or if it is, it may be too dirty or degraded to be effective. In either case, metal shavings and other grit wear down the engine parts, throw off sensitive tolerances, and potentially lead to catastrophic engine damage.

This can easily happen in the winter months, when cold, thickened oil is not allowed enough time to warm up and circulate throughout the entire engine. Many people let their cars idle for five, 10, even 15 minutes or longer to prepare them for commuting on freezing winter mornings. But the fact is that modern vehicles require nowhere near that long -- engine computers are programmed to find the right operating parameters after just 30 seconds of runtime. Anything longer than that is merely wasted fuel and unnecessary pollution from tailpipe emissions.

In a situation where start-stop technology comes into play, the car is already warmed up, along with its oil. So starting the engine again does not wear the engine down. In fact, several auto manufacturers are so confident of this that they plan to roll out start-stop technology across the North American product lines in coming years (the technology is already widespread in Europe). They see it as an easy way to reap gains in their model line-ups' fuel economy potential.