Originally Posted By: dnewton3
Originally Posted By: stchman
Originally Posted By: dnewton3
The UOA is telling you several things here:
1) Engine is in fine shape. The Cu is typical of many newer GM engines; it likely will subside and I'd not worry over this in the least.
2) The syn did nothing exceptional (nada, zip, zilch). The results are totally average and well within normal statistical deviation.
3) The TBN took a dive for only 5k miles, but without knowing TAN, it's kind of moot. TBN/TAN testing is pretty much unneeded if you're not going to greatly extend your OCIs.
4) The fluid was under-utilizied. Either greatly extend your OCIs and continue to monitor with UOAs, or use the least-cost qualified oil (warranty nod here) you can find on sale and stick with the OLM. Even the OLM is conservative, so changing before that is a total waste.
I knew that 5K was under-utilizing the oil. I am going to go by the OLM for my next change. I did the math. I have 75% left on the OLM and I've driven 2K miles. Simple arithmetic tells me that I should be due for an oil change at ~8K miles.
As far as the cost of oil, that's not a real concern for me. Since I change oil ~3X a year, if the oil costs me $27 when I could be spending $21 each change, that's not even a worth discussing.
As far as getting a TBN done, since this was the first UOA I've ever gotten, I was just curious.
Now armed with the info of this UOA, I will change the oil when the OLM tells me to.
Trying to guess the ending OCI now might be a fun game, and there is nothing wrong with making a bet with youself on the OLM lifecycle, but you really cannot fairly make that leap you made. The GM OLM is an "informed" system that uses a large list of parameters (coolant temps, run times, OATs, fuel loading, etc) to calcuate the OCI duration. The whole point of the OLM is not not have to guess when you should OCI. By guessing an 8k mile OCI now, you are not letting the system do it's job. Yes - you can use it as a game to "predict" when the OLM might pop up the "change oil" message, but planning your OCI, when only 25% of the OLM has expired, is not really the point of the system. Any significant change in operational conditions would result in a change in the OLM lifecycle.
As for the waste of the lube, as long as you can admit it as such, then go for it.
As I said, it was a ~8K estimate. I will change the oil when the OLM has ~5% left on it.
We are in a pretty good cold spell here in St. Louis, so I expect that the OLM should make necessary adjustments as ambient temperature has to be one of the inputs.
My thing is, the OLM does not know what type of oil you put in. I can only guess that the OLM is calibrated with AC Delco dexos1 synthetic blend.
