UOA looks OK. But why did you dig up an OLD UOA, Mr. Quackers?
I want to ask, however, if this is the infamous SL2 engine that tends to sludge up the piston rings? I am not intimately familiar with all the Saturn engines, so I need some help with identification here. If this is NOT the engine in quesiton, then the following comments do not apply.
If so, I would caution you against long OCIs. WHAT???
Did Newton just say that???? Yes - I did.
I looked at the SL2 engine in macro-analysis; it's known for sludging the pistons due to ring design, and I noticed that the ONLY predictor to having sludge formation was an uptick in oil consumption. There were no other tell-tale signs; no increase in wear metals, etc. The ONLY thing that will alert you to sludged rings is using more oil. Unfortunately, by the time that signal is present, it's already too late! Now - it's possible that compression is also effected by the sludging, but since Blackstone UOAs don't include compression numbers, that's data I'm not privy to.
Here is the macro data in regard to oil consumption:
3K mile OCI: .3 qrt
4k mile OCI: 1.6 qrt
5k mile OCI: 2.5 qrt
That data comes from almost 150 UOAs over several years. There was never a significant shift in wear metals or insolubles. Only the oil consumption shifts. The data I have is so scarce above 5k miles that I cannot get good statistical numbers; too few samples. At 7.5k miles, there is no ability for me to tell you what the long term effect would be. But looking at the escalation of oil consumption on a curve, it is fair to say it cannot be good ...
What I'm saying is that longer OCIs in this engine may not hurt anything in the short term when looking at wear, but longer sustained OCsI over many multiple events may well lead to sludge on the pistons. And by the time you get increased oil consumption, you've already got sludge.
There are a few schools of thought here; take your pick:
1) stick to 3k mile OCIs with a good detergent lube (PYB should be fine along with any other quality dino product)
2) try longer OCIs with a PAO syn that also has heavy ester dosing (PU perhaps?) and you can perhaps extend a bit
3) use a dino, along with something such as ARX, which has an tri-ester formulation, and you can perhaps extend a bit (although I would use a dose a bit higher than the "normal" maintenance phase amount)
The problem with #2 and #3 is that there really is no data to show how successful this may or may not be. Again, the problem is sludged rings. By the time you get into that high oil consumption, the problem is already afoot.
Turk had/has an SL2 ("creampuff"), and we went around and around about this a few years ago. Perhaps he could shed some light into this situation. I was unaware of the sludge issue until he educated me on it. He was going to use PU at 5k miles, IIRC. By now, he should have some data to show if it's been safe or not, relative to the oil consumption, unless his overall accumlated mileage isn't high enough to show disparity yet.
So - That is why, in this one case, I actually recommend shorter OCIs with a decent dino lube. If you know me (really know me), you realize that I let data and facts drive my decisions. While I am a big proponent of longer OCIs in most cases, this is one where it's probably not prudent. But that is not opinion; it's based upon data. And data does not lie.
