Originally Posted By: m37charlie
With respect Ibeg to differ. Using dealer oil in a BMWX5 35d (Castrol OE Professional 5W30) for the specified OCI, my TBN was 1.5 and TAN 4.8! Bad!
I now use Delvac 1 LE 5W30. TBN (virgin) 12.6 instead of 6.8. I think UOAs will be better.
I anticipate after almost 30k miles crisscrossing Australia even with ULSD my D1 SHC will show considerable decrease in TBN from 16. I am using standard D1 (TBN 12) for makeup, 2.5L/5500mi.
Charlie
You are the exception and not the rule. 30k miles is way longer than the typical OCI.
Most people OCI way before TBN would ever be an issue. All we have to do is look at the predominant quantity of UOAs to see that.
However, there are some intersting extended OCI examples out there. Look over this series of UOAs. All VPB, all the same engine, etc.
http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2179591&page=1
Note that the TBN varies from 5.x, 6.x, 4.x, 5.x, but the mileage goes from 12k, 14k, 16k, 18k. No make up oil; no bypass. These are four separate sump loads, not consequtive readings on the same load.
It's reasonable to believe that Valvoline intends to make that product with a fairly consistent add-pack, and that would include the TBN. Yet we see the TBN move a few points up and down, and the distance gets greater with each OCI. Also note how the wear metals move (or more specifically, the Al, Cu and Pb don't move even though the mileage increases. Fe typically always increases with use in most all equipment). However, it is fair to say that over approximately 60k miles of OCIs, there are also a few years of "ups and downs" at the production facility too; does the TBN move because of the useage, or because of variation of the virgin product? We really cannot say unless each load also had a VOA to match up with the UOA. Be serious, how many of us are going to pay for
TWO OAs to really track the TBN that closely?
Also, while the TBN has certianly dropped (from whatever actual starting point that we cannot confirm), it seems to "level off" even though mileage continues to increase. Now, I strongly caution that this is a VERY broad generalization, because only 4 UOAs are nowhere close to enough data to make a reasonable conclusion. But what is clear is that the degredation rate is not at all linear.
This is why statistical process controls mean everything and singular UOAs mean little to nothing if you're trying to find the "best" oil for your individual application. You cannot look at one UOA and definitively say "that XYZPDQ is the best oil". You can use a singular UOA to say that a particular fluid is doing a decent job, and may well be suited for continued use. But you CANNOT say one is "better" than another after one UOA. Just can't be done. I'm sorry if most don't agree with this concept, but that does not it isn't true.
We can make some general presumptions. Any oil that starts with 2x more TBN than it's competitor is certainly likely to last longer than the contrasted competitor. But can we say it will last 2x longer, just because it has 2x more TBN? Yes - probably. But not definitely. And what we see from this series of VPB UOAs is that even with very consistent inputs (same oil, same engine, same driving pattern, same maintenance plan, etc) we get very interesting, differing results.
To come full circle, the OP wants to know why XOM makes so many different syn HDEOs, and how similar (or dissimilar) the products are. My answer stands; there are different products marketed for different reasons, with different goals in mind for each targeted group. Some of them may be the "same" and only packaged differently, some not. But for most people, it's a moot point because they won't ever come close to the limits of the lube anyway. A precious few might, but most won't. So why worry about which one is "best"?
