joker97:
Ah I see, so it is a "direct fuel injection" engine. The people are saying because the [read: all] injectors are not circulated with engine oil the carbon builds up and craps it out eventually. The thing is, most advanced Euros are direct injected. Maybe they will all crap out too. [Note: I don't know, it's probably a luck thing.]
The problem is that with direct petrol injection there's no fuel vapour continuously washing the top of the intake valves. Exhaust valves aren't a problem because they get hot enough to burn it off. Some of the carbon probably comes from the EGR system, some oil and crap from the PCV system and slowly but surely it builds up on the top surface of the valves.
Gradually the cars economy and performance drops and it starts running like a bag of bones.
This can be cleaned, but involves removing intake manifolds and usually abrasive-blasting using walnut shell or a polymer grit. It's going to be much more expensive to do this with a complex forced induction v6 or v8 than a simple 4 cylinder normally aspirated engine because of time taken to remove everything to get access to the intake ports.
Other things equal, then this can be made worse by increasing cylinder pressures (forced induction / turbo) and using low friction materials in cylinder rings and bores to improve economy. Result of that is more blow-by with oil residues and the faster this build-up happens. It's not uncommon for owners of new-ish direct injection forced induction cars to report high-ish oil consumption, but then the makers tell them it's "within normal spec". IMO that's a load of croc - and the probable end result is as per the photo above - due to happen probably just after the car's out of warranty and then an ongoing maintenance nightmare as the engine gets older.
If you google this problem, then you'll see who those makers are.
A potential solution is to run a primary indirect injection system in the ports or throttle body. I believe Toyota are now doing this with some direct-injected petrol engines.
