My 2008 Audi A6 3.1L (3.2) FSI is experience on-going excessive carbon buildup on the intake valves (slightly different story than most posts)
Oil change interval is every 5,000 miles - not every 10,000.
Driving habit - 600 miles per week, average speed 70-90 mph in North East.

Summary of events:
* While using Castrol Syntec 5w-40 oil
-- with Exxon 93 octane fuel, miss-firing begins every 1,000 miles after valve cleaning and requires valve cleaning approximately every 4,500 miles due to violent shaking and permanent CEL.
-- with Shell 93 octane fuel, miss-firing begins every 1,000 miles after valve cleaning and requires valve cleaning approximately every 4,500 miles due to violent shaking and permanent CEL.
(Chevron Tektron does not really help when used every 3,000 miles)

* While using Mobil 1 0w-40 oil
-- with Exxon 93 octane fuel, miss-firing begins every 4,000 miles and requires valve cleaning approximately every 7,000 miles due to violent shaking and permanent CEL.
-- with Shell 93 octane fuel, miss-firing begins every 4,000 miles and requires valve cleaning approximately every 7,000 miles due to violent shaking and permanent CEL.
-- with Sunoco 93 octane fuel, automobile requires a manual valve cleaning at 10,000 miles. The automobile does misfire, but the event is so minor, it is a non-issue. However, I have noticed decreased fuel efficiency since the move from Exxon and Shell and when I hit 12,000 miles (oil change interval is 5,000 miles), the miss-firing becomes the most violent, as if the engine will drop on the street.
(Chevron Tektron does not really help when used every 3,000 miles)

* While using Mobil 1 5w-40 ESP M oil
-- experienced similar results to Castrol Syntec.

My question is, what is your recommendation in my situation and what oil should I use to help mitigate the issue since it does have an impact?

 

Does the 3.2 FSI have direct port injection, like the 4.2 in the newer RS4s? They have the same problem with carbon build up... Your best bet would be contact Audi of America to see if they have a permanent fix...

It turns out that with Direct Port Injection, the fuel isn't sprayed in the intake, which "washes" the carbon out. The carbon gets in there because of recirculated exhaust gases, used to help control emissions and regulate intake temps...

I know this doesn't solve your issue, but hopefully points you in the right direction... Welcome to the Forums.

Edit: One thing you could try is a couple SeaFoam treatments, see if that helps...

 

Bradtyler, thanks for feedback. I have been in contact with Audi America and the answer was they view this as normal maintenace. The 3.2 FSI is direct-inject as well. I tried seafoam with no real benefit (perhaps I used wrong vacuum hose?). The only fix is to use crushed walnuts or BG valve cleaning system. Any recommendation on a oil suggestion to help with my situation since it does have an impact?

 

I don't understand how the oil you use affects carbon build up on the valves, so I'm not sure what to recommend...

AoA states that manual valve cleaning every 10K is normal maintenance? That really doesn't sound right... Is it still under warranty?

 

AoA states carbon build up on valves is normal, why I have it worse then normal is unknown and unfortunate but it is my problem (made very clear by them). I purchased the auto with 20 miles on it, today I have close to 60k and I can say some oils do alleviate the issue better than others. This is why I'm searching for additional feedback.

 

you are having sort of misfire problem that does not sound like an oil issue