I started my 300SD and planned to let it run for several minutes because it sat for about a week. I forgot that it was idling and let it idle by mistake for close to three hours. Fortunately, the temperature gauge was reading only 85 degrees C when I finally realized that the engine was running and just before I shut if off. The engine was merely warm, just like after a 1/2 hour high speed ride. I took the car around the block to see if anything felt funny. Nothing seems to be wrong. Should I worry that I may have damaged something? Like turbo, for example? I heard that truckers let their diesels idle for hours, even days. I hope this 3 hour idle did no harm to this engine. This was in the evening, so temperature outside was around 50 degrees.