Idling vs. Starting and stopping engine.

HOWARDSFB

MEMBER
2004 TOYOTA HIGHLANDER

Recently my Dad and I were waiting in a long gas line at Costco and I would turn the car on and off again to move forward as people moved out of the station. He said that I should leave the car on as the act of starting and turning it off several times creates wear on all the parts involved, while I contended that idling causes sludge to build up in your engine and wastes gas. I eventually was able to get him to concede that turning your car off is better if you're waiting for someone at one spot, but he still said you shouldn't turn the car on and off again if you're in a line. Who's right here? How much damage is done to your engine while idling and how much is wear is created by turning the car on again?

1 Reply

KHLOW2008

MECHANIC
41,814 POSTS

If the wait is for short periods, leaving the engine idling would be better than turning it on and off. When starting, the ignition switch, starter motor and battery would be the ones most affected. The more you use the starter, the faster it is going to fail. Likewise for the ignition switch. When engine is started, there would be strains on engine internal parts as well as it takes time for the oil pressure to build up and it might be neligible but over long periods, it can mean something, especially when engine is cold.

Running the engine would waste gas but the sludge buildup is not the problem as it is neligible and even when engine is running at high speeds, sludge would also build up. Important thing is to have your engine oil replaced at the recommended time or mileage.

For any waiting period of less than 3 minutes, I would not turn the engine off.