What about engine Oil we used ?
Interesting Article
“Gasoline engines with direct injection of the fuel into the combustion chamber…suffer especially from the problem of the formation of carbon deposits…especially in the neck region of the intake valves.”
The document describes these deposits as a sticky coating of oil and fuel constituents that, once formed, serves as a base for further deposits, creating “a circular process, by which the coating thickness of the carbon deposits continuously increases.” Excessive carbon deposits “have extremely negative effects,” the patent application concludes, citing significant performance losses, sporadic ignition failures and, potentially, holes burned in the structure of the catalytic converter.
http://www.edmunds.com/autoobserver-...-adopters.html
I will ask my SA if he can take some pics of the before and after.