You should check out your cooling system. Maybe a new thermostat. My coolant is over 100 degrees F at the end of my driveway ( 1 mile ).

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Greg
2012 S350 BlueTEC 4Matic
2007 ML 320 CDI
2007 Leisure Travel Serenity
2006 Sprinter 432k
2005 E320 CDI
1998 SLK230 (teal)
1998 SLK230 (silver)
1996 E300D 99k, 30k on WVO
Previous:
1983 240D, on WVO
1982 300D, on WVO
1983 300CD, on WVO
1986 300SDL 237k, 25k on WVO (Deerslayer)
1991 350SDL 249k, 56k on WVO - Retired to a car spa in Phoenix
1983 380 SEC w/603 diesel, 8k on WVO
1996 E300D 351k, 177k on WVO

It takes me 4 miles to get the stat to open for the first time on warm days. cold days longer. This happens around 92C and then it drops down to about 82 and stays around there. Seems that for the most part it never closes, or at least not all the way after that. normal driving on country roads, 60 MPH. There is heat before then, just not max. and I think there is some electrical assist in W126 if you go to the max click.

The car being cold to the bone to start is the real issue. heated garage, no problem