Dear Car Talk:
When I was a young car owner (a long time ago), I was told that the worst wear and tear on an engine occurs when the engine is first started.
So, I’m wondering what your opinion is about the automatic “shut off” feature on many new cars. They shut off and then restart the engine every time a vehicle comes to a stop.
I know it saves fuel and decreases pollution, but does this decrease the engine’s life? — Roberto
No, it doesn’t, Roberto.
What you were told was true. When an engine is cold — when all of the oil has run down to the bottom of the engine overnight — it takes a couple of seconds for that oil to get pumped up to the cylinders, bearings and valve train.
And, during those couple of seconds, those parts are moving but not perfectly lubricated. That can cause excess wear and tear.
That’s why we used to warn people against revving the engine the moment it started — which was a bad habit a lot of people engaged in.
But, if the engine has been running recently — meaning in the last couple of hours — the oil is already well distributed and the oil passages are all filled up. So, during a two-minute shut-off at a stoplight, those passages will remain filled with oil.
Plus, plenty of oil will still be coating all the engine parts very well, protecting them during the next engine start.
If you were to be stuck at a traffic light that was red for several hours, my answer might be different. I would also suggest you explore options for working from home. But warm engine restarts are not a problem.
The other thing that’s changed since you were young is that engine oils are vastly improved. When you were a kid, we used thick, gloppy oils that took longer to circulate, especially when cold. You may remember terms like 20W-50, which acted like a heavy, 20-weight oil when cold and a 50-weight oil when hot. Now, cars use 0W-20 or 5W-20 weight synthetic oils that spread very quickly, even when cold, and coat and protect the engine parts better than ever.
So, cross this off your list of things to worry about, Roberto. Maybe replace it with worrying about the monthly price increase just announced by Netflix.
Got a question about cars? Write to Car Talk write to Ray in care of King Features, 628 Virginia Drive, Orlando, FL 32803, or email by visiting the Car Talk website at www.cartalk.com.
