"Heavy Driving"
 

[FONT=Arial]I've got a sticker on the drivers door of my 99my which basically says "let the engine idle for 1 minute after heavy highway driving"

What constitutes "heavy highway driving"?

I usually let the engine idle for a minute if I've been caning it :norty:
but is it really necessary after say a 10 miile journey to/from work where the revs have not been above about 5000 rpm?

Being a bit naive in the technical department - what is the reason for the sticker - I've never seen it on other cars...

The sticker is saying " If you've been using boost more often than not on your journey then let the turbo cool down before switching off the engine"

Basically when the turbo has been worked hard it gets so hot that it needs constant recirculation of water and oil to stop the turbo and its bearings from overheating.

If you were to switch the engine off then the oil and water pumps stop working, hence the oil in the bearings just sits there and gets so hot it burns, leaving carbon deposits on the bearings, which in turn causes the bearings to fail and the need for a turbo rebuild.

Letting the car idle for a minute or so will cool the turbo sufficiently so that it won't burn the oil upon switch off. However if you drive the last few minutes of your journey off boost the turbo should be cool enough not to need to let it idle at your destination.

The usual scenario for the validity of this sticker is when you've been making progress on the motorway and pull over for petrol / dying for a pee ;)

Hope this helps

Thanks Jay m A

That makes sense. At least I've learned something new today