Quote Originally Posted by yebo View Post
The only 2 ways to "cook" a turbo are 1.) to shut off the engine while the turbo is still hot (no cool down) and 2.) to immediately shut off the engine after pressing the accelerator pedal down, like what old school drivers used to do (vrooom vrooom then shut off engine). The 1st is obvious, the cooling oil stops flowing while the turbo is still hot, causing the oil to "cook" in the bearing. This causes "varnishing" of the oil, leading to smaller tolerances which eventually lead to oil starvation. The second, this causes the turbo to spool up, then when the engine is immediately shut off the turbo is still turning at thousands of rpm and there is no longer any oil flow to lubricate it. Result is a "cooked" bearing.
That's what I thought. I saw turbo engines idle for long periods without ill effect.

I did the same with my gasoline Mitsu 4G63-T engine, especially during cold winters when it took 10 minutes idling just to bring the engine RPMs down to normal. It took even longer for the temperature gauge needle to start moving which could take another 5-10 minutes of idling. I'm not 100% sure because I usually started the car and then ran back inside the house. Brrrr.

But, I think we're in the same page with regards to the engine shutdown part where the greatest risk for turbos is at.