I just bought an Isuzu D-Max turbodiesel. There is no water jacket on the turbo, which put me to wondering. I had a Porsche 944 Turbo that did have a water jacket, as well as a pump that would keep the water circulating briefly after shutdown to prevent the oil in the turbine being cooked. Nonetheless, I habitually let it idle half a minute or so before switching it off, especially if Id been rawhiding it. The D-max diesel has a sterling reputation so Im guessing its exhaust is enough cooler than in a gasoline motor that coking is not a problem. So is it pointless to go to the trouble of an idle cool-down before switching it off?