I have a 2007 335i coupe with 17k miles on it, 6 spd manual. I've noticed a thick black soot of carbon buildup on both exhaust tips, which builds up in very short time between weekly washings. BMW Seattle claims this is "normal", BMW NA claims "this is normal". I'm not buying it. I suspect this has something to do with a direct injected turbo motor, but you don't see black tailpipes on Audi A4's....so do you folks think this is "normal"?? If it looks like this at the exhaust tips, I can't imagine what it looks like further upstream.
It's normal. If you're worried about carbon buildup further upstream, you should let it loose every once in a while, but since it's a 335i with a 6-speed, I'm guessing you already do that, more often than you care to admit. You shouldn't worry about it.
Yet another "it's normal". I don't recall my 2007 E90 328i with the same amount of soot on the pipes but then the 335i is in another world itself.
I have noticed this on my new 2011 335xi as well. The car is not yet fully broken in yet. However there is more soot on the right(passenger) side than the left.
It is normal, all my cars do it too. From what I understand, the reason it is on one side more than the other is because most of the exhaust only goes through the one side. The other opens up at higher RPM, that is when you can hear the engine more.
