What is your engine temperature? Should be right around the 80C/175F marker after driving a few miles.

If it is significantly below that, your thermostat is probably stuck open and the engine can't heat up to optimal operating temperature - this is bad both for you and for the engine.

Feeling the hoses won't tell you anything, the difference between 130 F and 175 F is hard to tell since both are painfully hot to a human.

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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