think of that knob has a manual choke. As mentioned, it really is needed in the colder temps. Set it as low as she can with out the car stalling when you first get her started.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member