Engine cooling to avoid heat-soak when engine is off.
This is my set up in action where I wired the electric fan and the aux water pump to cut on at 91°C even when engine is off to avoid the extremely high temps in the engine. The temps come down in a matter of seconds.

https://drive.google.com/file/d/1VP8hnn6UOBjw-Fb1D9BsJcjD4g8FkB6v/view?usp=sharing

https://drive.google.com/file/d/1ckmyET4KMGXuI8WkP5f1vSvz3muRdhO1/view?usp=sharing

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1990 190E 3.0L

Not a bad idea. Most of burned on oil varnish you see inside some engines happens after the the car is parked with a hot engine. I just made a habit of popping the hood when I get home.

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CENSORED due to not family friendly words