Just replaced my W210 battery with a genuine MB - it was less than $200 over the counter. It definitely has a vent tube. There are vent ports at both ends, so the shipping protective plate for the + terminal has a breakaway plug that you are supposed to insert into the unused vent port.

I too get about 13.3-13.5 V on the climate display under normal driving conditions. Really need to hook my Fluke 87 up directly to the battery and see what it reads.

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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