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This has been BMW's recommendation for over 10 years.
It's been the recommendation of virtually all automakers for over 10 years.
It's been Consumer Reports' recommendation for over 10 years.
Idling doesn't warm up anything but the engine; and diesel engines take forever to warm up. Idling increases emissions, especially of HC and CO, since a cold engine has to run rich. It wastes fuel.
The shift to multi-weight, 0/5W-30/40 oils gets the oil through the engine very quickly; unlike the older single-weight oils. If you let the engine warm up, you still have to drive "moderately" to warm up the transmission and other drivetrain components; why not do both at the same time?
This is in the 2001 3-series manual, p.63:
"Do not allow the engine to warm up by
leaving it running while the vehicle
remains stationary. Instead, begin
driving immediately at a moderate
engine speed."
Last edited by floydarogers; 05-02-2014 at 06:33 PM..
Reason: add manual ref
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