Q5 Carbon on exhaust tips
#11
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Join Date: Dec 2013
Location: pennsylvania
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I think your dealer is dyslexic. Premium fuel in Germany is actually 98 RON, which equals 93 AKI (the octane scale we use in NA). Regardless, octane has nothing to do with tailpipe soot. Soot is most likely a function of the DI fuel delivery and DI engines typically run very rich on cold starts. If your driving pattern is typically lots of shorter trips with fewer long ones there'll be more soot. Also, any oil consumption will contribute to fouled tips.
I've owned four vehicles with DI, and the only one that didn't have a lot of tailpipe soot was an F150 which was 90% highway driven.
I've owned four vehicles with DI, and the only one that didn't have a lot of tailpipe soot was an F150 which was 90% highway driven.
#13
AudiWorld Super User
#14
AudiWorld Super User
In the case of the exhaust pipes, if the carbon is old and baked, Never-Dull is a lot of work but at least it won't scratch the chrome plating. It comes in SECOND PLACE to Blue Magic and #0000 steel wool, which is the best.
Last edited by ELEVENS; 01-10-2014 at 03:35 PM.
#15
AudiWorld Senior Member
Ours is driven short to moderate distances with an occasional longer haul. I'll be keeping an eye out for build up but I think it would have appeared by now. Good luck with getting a solution to your issue.
#17
#19
AudiWorld Super User
it's what Elevens sez: it's the toxic crap created by the DI engines. It's very evident on both our cars.
I've found that you've got to attack it every week when the car is washed. Then removal isn't too bad. I treat it just like the 5th wheel and use a bit of wheel cleaner and a tooth brush to lift the stuff off. If it's hasn't been cleaned for a long time, you will need to attack with the #0000 steel wool and some type of cleaner or polish. Frequent cleaning is mandatory to keep it looking as good as the rest of the car.
I've got a dozen different metal polishes in my basement and have had measured success with all, but nothing truly impressive. Someone over on the detailing site suggest the Chemical Guys' product called Metal Shine Extreme Polish & Protection for Metal. I bought a bottle of this six months ago and have been really pleased with it in a number of applications. And it does appear to control the build up of the toxic goo in the following weeks and I can't report that with any of my other polishes.
I've found that you've got to attack it every week when the car is washed. Then removal isn't too bad. I treat it just like the 5th wheel and use a bit of wheel cleaner and a tooth brush to lift the stuff off. If it's hasn't been cleaned for a long time, you will need to attack with the #0000 steel wool and some type of cleaner or polish. Frequent cleaning is mandatory to keep it looking as good as the rest of the car.
I've got a dozen different metal polishes in my basement and have had measured success with all, but nothing truly impressive. Someone over on the detailing site suggest the Chemical Guys' product called Metal Shine Extreme Polish & Protection for Metal. I bought a bottle of this six months ago and have been really pleased with it in a number of applications. And it does appear to control the build up of the toxic goo in the following weeks and I can't report that with any of my other polishes.
#20
Actually octane can effect it. Not sure if Audi does this but many cars are programmed to add fuel if it detects knock, and by running slightly rich it can leave deposits on the exhaust tips and the back bumper of the car. They really do need premium if you are going to push it at all. Under a load it could just be throwing a bit more fuel.
I do want to try the wd40 trick. Never done that one.
I do want to try the wd40 trick. Never done that one.