Hmmmm, that kind of begs the question, what is the best 4 cylinder matched to a luxury vehicle in history? Could it be the original M3? Maybe something older? I agree that 4 cylinder and luxury don't really match up well. In fact, I think the best luxury vehicle is likely suited for an EV powertrain. Just smooth power delivery, hush quiet. If they could just make them with enough range and capable of dealing with cold weather.