I'm looking at a 2016 E250 Bluetec. 28k mi, still under the manufacturer's warranty, but not CPO. It's eligible for MB's extended limited warranty. My concern is with all the DPF/AdBlue components. I've been told that they're prone to failures after 50k mi or so and that the extended limited warranty or even the emissions warranty won't cover those failures. I've done searches about their reliability and asked around and I've heard everything from how bulletproof and trouble free they are on one end to how troublesome they are on the other end. I assume the truth is somewhere in the middle. I've seen a few posts here gushing over the GLK250 which has the same engine, but not as many about the E250. Don't worry, it wouldn't be replacing the 300SD, it's an heirloom that's going nowhere! But I know the OM651 is a completely different beast than my OM617 and want to know what to expect should I purchase it.