From the MB fluid sheet on Startek

http://www.startekinfo.com/StarTek/outside/9511/?requestedDocId=9511

Diesels older than 1997 can use 229.3 or 229.5 (or API CF-4 or CG-4) which is what M1 Turbo Diesel Truck meets.

Diesels 1998 and newer need 229.51 oil. The only Mobil product that meets that is the now discontinued M1 Formula M ESP 5W-40, or the replacement ESP X1 0W-30.

From 1998-2004 the need is due to proper operation of the FSS/FSS+.
From 2007+ the need is due to to the low SPAsh content of the oil so it doesn't kill the DPF. Doesn't hurt to have this in the 1998+, they have a catalytic converter.

According to the viscosity chart in that document, both 0W-30 and 5W-40 are approved for all temperature ranges.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech