I was pondering engines and reliability as I drove home up I-95 North. Is there a general consensus on the most reliable Mercedes engine made in the last 10 years? I wouldn’t think it would be a 4 cylinder, but maybe the V6 or V8. Does anyone know?

I nominate M276.

OM654 or m276 as mentioned

Old? PLENTY. I'm missing a huge scope of 80's cars but those have some incredibly dependable powerplants save for the biodegradeable harness 20+ years later.
100 (the original 6.3) 102 (190E)
112/113/113k
120
271 (this is crazy reliable especially considering how behind MB was in servicing their own cars of the period)
272/273 that were not affected by the idler problem

New? just a handful. I'm actually kind of leary about new MB of any sort in general.
276
157
177/178
275

I don't care what anybody says the v12's are actually mad dependable for both what they put out, the 1st ownership experience, and cost-per-year upkeep. Once you include the sometimes stupid cars they're put in, with ABC suspension, yes it absolutely sucks to get to some parts and some parts (alternator, AC, water pumps) are expensive but these are a one-time fix and the parts being MB genuine only for certain cars means everything is working as it should. 13L of oil keeps em running cool, for a long time, and with a somewhat long service interval.