Even though MB does not recommend fuel additives, they do say to add kerosine to the diesel in the winter time, if winter grade diesel is not available. I use Power Service diesel additives. $4 gets you a bottle that is good for 100 gallons. They have winter and regular formulas. The winter one prevents diesel from geling. Both formulas increase the cetane level in the tank.

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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