diesels do take forever to warm up - in my 330d, i can drive the 3 miles to the station, and then the three miles back again before i get any heat out the vents. even worse on cold days.
yoinked from some yank forum:
Several reasons – a couple of which the others already touched on:
1 – Most significant is the diesel engine’s higher fuel efficiency. Compared to a gasser, a diesel sends considerably more mechanical energy out (as work at the flywheel), and loses less energy into the coolant (in the form of heat) for every gallon of fuel burned. Depending on the engine, 30 - 40% less heat is lost into the cooling system than in an equivalent gasser. Net result is longer warm-up times.
2 – Except at wide open throttle, a diesel operates with considerable excess air. This excess air carries a portion of the engine's waste heat out the exhaust. Most significant at idle and light load in cold weather – some diesels will NEVER warm up if left idling in cold weather.
3 – Finally there’s simply more iron and larger cooling system in a diesel. There’s just more cold stuff that’s gotta be warmed up! ...FB