Any update on this?, a friend is having exact same issue on a 2012 GL350 with 120K. He religiously changed the oil with spec and he's losing a quart of oil ever 1000 miles, and dpf regeneration is happening every few hundred miles. Dealer is advising him to replace engine and dpf, and extended warranty company is trying to rip him off by not paying for the repair. Please help us find out what the issue is, because nobody believes it's bad rings like the dealer has suggested, and it shouldn't need a motor. Thx.