It is stock had a brand new radiator put in recently its a v6 mechanics or thinking oil filter housing
I agree, I mean if there is no evidence of coolant getting into the engine block, and the engine is not overheating. (Or sounding like a running diesel.) Then I'd just change the oil and coolant (along with the oil filter) while examining everything for any abnormalities.From the completely un-educated here, it may just be sludge that builds up over a number of years/miles.
My V6 is about to roll 200K, when I had my cooling woes last year got the milkshake gunk in the rad cap.
Cleaned it up and haven't seem it since.
My oil is changed every 7000K, the coolant was swapped out at 140km when I got the car and 3-4 times more because of my cooling woes.
Not much more here to help other than....that's life owning a G8, clean it up and keep an eye on it.