10Year+ Supporting Member
I do not know if this is critical in car turbos or not. I have owned several turbo diesel pick ups and class 8 road tractors. The rule of thumb for them was to give the turbo a few minutes to "cool down" and rpms to come down by letting the engine idle a few minutes before shutting it down. This kept good oil circulation in the turbo during this idle period. I have never owned a turbo gas car so I may be completely off in my thinking.