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Originally Posted by macafee2

I always let the car idle after a long run and particularly if towing, it may even be in the handbook, 2 -3 minutes. I also lift the bonnet to let the heat out if I have been towing. Strangely or sadly no one has ever asked when I'm parked at motorway service with the caravan attached and bonnet up if I am ok, they just walk past.

macafee2

The reason for the tick over bit is to make sure there is oil in the turbo bearings. It's not really to dissipate very much heat though it helps.

Some folk have the engine revving as they switch off. The turbo could be spinning at around 80,000 rpm.--

As the engine stops the oil flow stops too. The turbo then slows down to a halt with NO OIL PRESSURE.

With the engine ticking over for twenty seconds, maybe, the turbo is then spinning very slowly. As the engine stops the turbo is very quick to follow leaving plenty of oil in the bearings for the few seconds it takes for the turbo to stop.

In fact the turbo body with no air flow to help cool it will actually get hotter but not hot enough to damage any components.