Q More and more manufacturers are touting stop/start as a feature to save fuel, but I was always told that most engine wear occurs on start-up. Are we trading a few cents’ worth of fuel savings for reduced longevity and more expensive engine repairs down the road?
A A lot of wear does indeed occur on start-up – that is, initial start-up. When a car sits for more than a few minutes, the bulk of the oil in the bearings, the cylinder head and the passageways flows out and down into the oil pan, pressure drops to nothing, and the engine’s wear surfaces become vulnerable. Stop/start systems are designed to turn off the car when sitting for more than a few seconds, then instantly fire it up using a heavy-duty starter when the brake is released and before the accelerator is depressed. The idea is to save fuel and dramatically reduce air pollution in major cities.
Now, does this expose the engine to additional damage? Probably not. Engines are always tested to failure in modern engineering – put through the worst possible conditions and with every conceivable use scenario. As a result, engines designed to work with stop/start have revised bearing and oil-passage designs that accommodate low oil pressure. If you turned off and started a regular engine at every stop, the wear would take its toll over time because it wasn’t designed to work this way.