1. Agree about a short (15sec-1min) period of only idle prior to moving off. Put you phone away, sip coffee, turn on the audio, whatever

2. I discount the manual due to the fact that the recommendation is not based on what is best for your car, but is based on a composite of factors including pollution/green factors. A car idling in the driveway for 20 minutes is a polluter, and a responsible mfg should discourage.

3. However, idling the engine will not warm the tranny adequately, and hence you can warm up the engine - looks hot, right? yet the tranny is still relatively cold. You can inadvertently abuse the tranny in this situation.

So I guess I'd say 'warming a bit and driving is good'...and 'letting it sit is also OK, but the drivetrain is NOT fully warmed in this way'

Way to complex a discussion for a BMW manual though... especially now that BMW has no way on the diesel to measure engine temp. Idiots.

A