Originally Posted by immiketoo
So after reading this thread, I spoke to my buddy who is the service director of my BMW dealer. He told me this is a legitimate issue with 335s and cars that share that motor due to the carbon buildups that occur in the intake system. He also told me that it is not recommended for M3s as they tend not to could like the 335. He also confirmed that it is a dealer recommended service that is NOT part of the service agreement. He's a straight shooter and I didn't detect any BS. Just seems like a recent addition to service a developing problem on certain engines to keep performance tip-top. FWIW.
Due to the DI configuration of the N54, using fuel cleaner such as techron, will help keep the fuel system, injectors and pump clean..but will do nothing for the intake valves..the cleaner/fuel mixture is sprayed directly into the cylinders bypassing the intake valves altogether.
For the M3 since it uses port injection using a fuel treatment will help clean the intake valves as well as the injectors, the fuel pump etc b/c the fuel mixture is sprayed over the valves.
This is not BS..over time fuel will leave varnish deposits on crucial areas...every BMW manual I have read always recommends using techron..I have used it for yrs with good results..as a ref I have a 170K mile car that still has original injectors and pump..always used techron in it.