I don't know if I'm just paranoid/especially sensitive lately or what but I've noticed that while at idle after driving for a while, or cruising between 20-40 mph, it seems as if engine noise has increased (vague, I know). No real difference in sound/new noises, just louder. Even with music cranked up fairly loud, I can still hear it. I'm guessing this is insignificant but I'm just throwing it out there for comments.
'13 Iridium Silver C63 AMG Sedan (540 hp; 500 lb-ft)