I have read many BMW forums and threads to learn that BMW NA does not approve of such. I live on "Devil's Island" (Roundel, Nov 2013), 25 square miles, where a typical winter day's drive might be ten miles, hardly enough to warm an engine. Indeed, in ten winters my previous diesel VW TDI did not ever reach normal operating temperature of 190°F indicated. Is there any positive experience with a block heater installed on a diesel BMW? I am not so concerned with starting ability as with overall longevity, economy and comfort. My VW started reliably at -25°F, once at -35°F. My 30 y.o. diesel tractor without glow plugs starts at 0°F.
What kinda of block heater are you considering since magnetic, in oil, coolant with circulation pump? Main thing you would want to heat is oil since thats the only thing that would effect the longevity. The other is once and awhile you should drive the vehicle for a extended drive so it can go into regeneration mode so the particulate filter doesn't clog up.
"... since magnetic, in oil, coolant with circulation pump?" Since they what, please? My TDI did well with a Zero Start (by Frost Heater) IIRC 1 kW convection/thermo-syphon coolant heater. In the 100K miles after the intake manifold was replaced with a clean one, after the EGR duty cycle was minimized, I saw no evidence of CBU. Thanks for your response. It brings up another newbie question. How can I tell when the engine is fully hot, IOW what precisely is an "extended drive?"
Sorry about that was tired when I wrote that. I meant to say which one are you looking to get? I recommend oil for heating the oil since that will give you the best benefit to the engine but the coolant like you mentioned will work well. There is no good way to tell if you engine is full hot. As for the extended drive basically just drive a 30 min high way trip some where and be a rough on throttle this will get regeneration going and clean out the DPF (diesel particulate filter).