I've always heard from several friends that its good to keep your car on idle for about 5-10 minutes after running at high speeds on the highway, is that true? Or just a waste of gas!!?

 

I would've thought that would be the case of turbos to allow the oil to cool down?

 

I agree with you -- had a friend with an Evo and even after pulling the key out, his Evo would stay on for about 5 mins to cool things down. I really don't know cause my SA mentioned to me that I should do it since I drive on the highway everyday to go to work. Really don't know what to believe.

 

Myth, in fact the engine gets hotter at idle than at highway speed (coolant temperature as measured by my Scanguage II). At highway speed my coolant temperature is approx. 180*F, at idle the temperature will go to 210*F before the electric cooling fans come on.

 

It is a very good idea on a turbo engine...after a few min of driving hard, the turbo will actually glow red-hot. But without a turbo, like someone else said...you're engine will get hotter if you let it sit and idle.

 

Myth solved! Since you've done an actual test! Can't wait until I see my SA next week.

 

No, but it would be a good idea to let the car warm up before you drive it hard.

The turbo issues have already been said.

 

Just to shed some light on the turbo thingy...

Most turbos are cooled by the oil. Shut off the engine, and you shut off the oil supply to it. By letting it idle for a few minutes, it does a couple of things:
1. It lets the turbo cool down, and
2. It keeps the oil supply running to the turbo which keeps it from cooking the oil.

This cooking of the oil is known as coking. It will actually destroy the oil and turn it into a gunk that you don't want there. This gunk will eat the bearings and cause a real mess.

Since you don't have a turbo, you don't have to worry about this since when you shut the engine off, everything else stops, too. As previously mentioned, you want to take care on starting your car. Don't run it hard when you first start out. For me, I live in a neighborhood where the speed limit is 25 mph and it is 0.6 miles to the nearest road where the speed limit goes up to 45 mph. I'm on this for about 2 miles, and then I hit a parkway where the limit is 65 mph. I take it easy as I head out each morning. By the time I hit the parkway everything is fine, and this was true even when the temperature was down around 10 degrees outside.

FWIW - according to my ScanGauge II, my normal operating temperature is 173-175 on the road. In town, it can climb to just over 200 degrees.