MyBigToy said:
They had problems with the early 3.6L V6's. It appears part of the issue was going to longer oil change intervals, at least on the Enclaves. We could have gone 10K miles between changes if we had waited on the "change engine oil" message. GM "recalibrated" the oil change interval down to 6000-6500 miles in 2009 and the majority of the stretched timing chain issues appear to have gone away. I used nothing but full synthetic on a max of a 6k mile change interval, mainly Pennzoil Platinum, on the 3.6 since it's been shown through UOA to shear the oil pretty badly. Pennzoil Platinum and Ultra were particularly good about holding up against that shearing in the 3.6.
This is part of my understanding, as well.
The engine in our CTS is also victim of a common oil consumption issue where I have to add a quart every two weeks or so.
This appears to be from another poorly designed PCV system from GM.
We found that some of the oil that was missing from the crankcase got deposited in the plastic air intake tubing AHEAD of the throttle body.
Imagine my surprise when I took that tubing off to clean the throttle body and dumped a good portion of oil onto the ground from a device I expected to be oil free.
Now I check the tube at regular intervals and clean as needed.
Some people on the Internet have resorted to adding an oil catch can in line with the PCV hoses to deal with this issue.
Anyway, by adding a quart of fresh oil every couple of weeks to keep the six quart crankcase full helps to keep fairly fresh lube in our engine.
Or so I keep telling myself.
In addition, ever since the timing chain repair, I now change the oil at 50% on the oil monitor instead of trying to stretch it out longer toward 0%.
With the crappy PVC system, the oil tends to get much darker, much sooner than the oil in my EXT anyway.
I would think that if someone wasn't paying very close attention, they could trash one of those engines in no time.
The car runs and handles too good to get rid of, but it does take a little more attention than I would like.