Yes, lean cruise can be taken pretty far because the injector timing can be altered which greatly reduces the risk of detonation. The pistons that I have seen do have a strategically located and shaped recess that serves as a mini combustion chamber. It is very similar in concept to the pre-combustion chambers used in some diesels. These features also allow for even higher compression ratios without the increased tendency to detonate. I am also wanting to think that piston squirters were a feature on the 3.6 high-feature v6 and it's other variants. I'll see if I can verify that info later. Anyway, I do have a "teaser" pic that I can share that is a pic of a direct injected v6. If you look real closely you can see a couple witness marks on the outer edges of the dome (yeah that's right I said dome) from the intake valves making contact. This thing saw 20k mile intervals on regular old conventional oil because that's what the oil life monitor said and believe it or not GM says that's perfectly fine. This is the result of going by the "approved" maintenance schedule which was new cylinder heads and timing chains all before 100k miles.


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