Cadillac SRX First Generation Forum - 2004 - 2009 Discussion, Shell Gasoline and Intake Valve Deposits in Cadillac SRX Forums; It's true. It's clean. If your valves have deposits, you're using the wrong gasoline. Period. This engine has no silly ...
It's true. It's clean. If your valves have deposits, you're using the wrong gasoline. Period. This engine has no silly "catch can," has a high oil consumption rate, has original valve stem seals, has seen factory OCIs using some dino (but mostly synthetic) oil, and has a history of light sludging.
Anyone who tells you otherwise doesn't know what they are talking about.
On a Non-DI you are correct, we have heads in here with 140,000 miles on them and not a spec of deposits anywhere the fuel spray makes contact. But the oil causes detonation, less power, and carbon build up on the pistons and combustion chamber on port injection engines so the benefits are many for all engines.
But the DI engines are totally different as the fuel never touches the intake valves
Here is a port injection engine showing how the fuel is constantly drenching the intake valves so the detergents not only keep them clean, they also keep deposits from forming in the port where they touch as shown here:
And a DI:
There is not a DI engine made that the fuel touches the intake valves in any amount that the detergents can have any effect.
I tear these down non stop and we also do on the car manual valve cleaning.
Here is a before and after of the manual cleaning:
It is critical on any non DI as far as valve deposits. Now piston ringlands will still build up oil burn residue and cause the rings to not move freely compounding the oil consumption issues, but there is no disputing the effect on intake valves.
Here is an example of a DI engines run with top tier fuels:
That is where stopping the oil ingestion is critical.
I am not going to start another flame war, and get ready for another core dump of information, but GM says their direct injection engines do spray gasoline on the intake valve precisely to reduce these kinds of deposits that other engine manufacturers see.