I think if you do some reading you will find that engine failure is the least of concerns for amg or really any type of engines that mercedes makes. That said the past failures I've seen are always related to engine electronics from the evil Bosch folks. But maybe given the hammering mercedes got in the early part of the decade about quality control and their acknowledgment that "it's the electronics stupid" then maybe they've gotten the electronic suppliers in order. Certainly my dealer has told me there just hasn't been any issues with the w221.