exhaust leaves black residue/gunk?

Question

i have a 2005 Chevy Avalanche Z71 LT. the engine is a 5.3 V8...i have a 2 chamber Flowmaster exhaust (cat back)...ive had the exhaust on since 2 days after purchasing the truck (06/05)...recently, i noticed a blackresidue/gunk above the chrome exhaust tip on the back passenger side of the bed. its never done this/been there b4. is my engine running dirty???

i change the oil every 3-5K miles (i have EZ Lube put in Mobil 1 synthetic every time which is s'posed to last 5K)...i have al the fluids changed according to how many miles are on my truck (according to EZ Lube)...any suggestions to stop this form happening????

should i be concerned about possible engine damage/failure etc etc...

any suggestions of a good product to get it off???

THANKS!!!!

Answer 1

If you also have a little black smoke along with it your engine is running a little rich. Black smoke indicates unburned fuel and this could cause a black stain.