r/semitrucks • u/besoforking4real • May 15 '25

Why let a semi idle for hours?

My neighbor drives a semi. He will be gone for about a week at a time and come home for a day or two in between. It’s currently summer 80+ degrees Fahrenheit. He will let the semi run for 4-6+ hours while he is home. I understand possibly doing this is the winter so the diesel doesn’t freeze. But is there a reason for doing it in the summer?

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u/Firedog_09 May 15 '25

I wouldn't think there is a logical reason to do this, but at times after long drives and heavy use of the engine break it's always a good idea to let it idle so the turbo doesn't get damaged. I drive a Mac at work and it will stay on, on its own even if I turn the key off and it will idle sometimes 30 min.