There's is not going to be some magical forumla to predict the oil temperature at the turbo based on the coolant temperature or even the oil temperature at the sensor. There's too many factors; namely, how hard you have been driving and cool down.

If you drive the car hard, say at a track event, both coolant temp and oil temp will go up. However, your coolant temp will decrease faster than the oil temp. So while the coolant temp is down the oil temp will still be high; and at the turbo it could be very high. Then when you shut the car off, the oil and coolant quit flowing and could create a problem at the turbo with the heat soak.

In most instances you won't *need* the system running. However, after running a track event in 100F heat for two days, oil temps at the sender were getting above 275F. And while the car was cooled down as best as it could be in a parking lot, at no point did mine (are anyone else's) after-run system come on. If it's not going to come on in that heat and those conditions, when will it?? That's why I wanted to, and did, this change.

I understand what your asking. Does it really help? Is it really needed?? Certainly understandable and good questions. But the answers are quite complex with an infinate numbers of possibilites.

The question I posed when deciding was; Will it hurt anything to cycle coolant through the turbo when it's not needed??? NO! For $30, the piece of mind is worth it for me. Maybe it's not for you.

Current Audi Count ---> 5


Previous Audi Count ---> 7

In spite of dealers; I still love Audi :-)