As soon as the oil pressure is up get going.  These diesels will not warm up
idling and must be driven, idling a cold enigne will carbon it up.

My 80 300SD warms up about as fast as any other car I've owned.  In
fact, I'd say I get cabin heat faster in this car than in most others.
I've always driven it after starting up, without waiting, unless it's
very cold, like under 20.  Then I keep it idling a little faster than
normal, just at the point where it runs smoother for a minute or so
before driving off.  Then I take it easy for the first 5 mins or so,
while it warms up.

If yours takes a long time to get to normal temp, I'd change the
thermostat.

Start it and drive off.

My diesel takes longer to reach 80 degrees C. than my gas car but that's
the nature of a diesel's thermal efficiency vs. gas engines, IMHO.

Thomas Lambach
'80 300SD, owned since new

I wait about 30-45 seconds on my 81 300td.  The oil is always pegged, and
the engine has a good, solid sound.  I agree that it's a Looonnnngggg time
to get the thing warmed up while idling, even on a warm day.  However, I do
try not to jump out of my parking lot and do 60 at full acceleration while
cold.