Frank,
I will give you my honest opinion about you oil based on your analysis report.
1. Based on relatively high AN of the new oil and after being in service, it seems that your oil is blended with Group 1 base oil. In addition, relatively low initial RPVOT (310 min. for new oil, when most Group 2 turbine oils have RPVOT at minimum 800, and some in range of 1200 and up to 1800 min). Also, the presence of Zinc (and phosphorus and sulfur) lead me to believe that you have ZDTP type of antioxidant, which was generally used (and probably still is somewhere) for blending Group 1 turbine oils, rather than exclusively an ash-less additive package. If this is correct, then I don’t know how reliable RULER analysis would be for you. Maybe Bob K. can shed more light to it.
2. From my experience, I have seen the initial RPVOT (new oil) drop after the oil has been in service for awhile. However, after this initial drop, RPVOT establishes itself at some lower level and remain on that level for long time. If you look at Zinc concentration, you see the same pattern – drop from initial 86 down to upper 20 level, and remain pretty consistent at that level. That also support my thought that you probably have Zn-based antioxidants. Of course, they might be some ashless-type additives added too, but they are not exclusive.
3. Your Kleentek filter works fine. The cleanliness reported on 30 Jul, showing worst code than the one from 7 days earlier, may be affected (contaminated?) during sampling & handling, or the same sampling procedure was not utilized (e.g. draining at the sample port inconsistent?). I say this because both the Gravimetric Patch analysis and Ultra Centrifuge suggest that the sample from 30 Jul is cleaner than the one from 23 Jul.
4. I don’t know what to make of you RULER analysis, but you don’t have to sweat (yet!) too much, because your RPVOT shows approx. 35% of the remaining life, and condemning limit is when starts dropping below 25% of the remaining RPVOT. I have a sense that RULER lovers think very low of RPVOT (like, it is inconsistent and not trustworthy analysis). But guess what, in RULER literature it is suggested to run RPVOT (yes, the same “unreliable” RPVOT) whenever RULER comes down to 25% level – to check for the “Remaining Oxidative Life estimation”. Some folks love to have it both ways.
5. The one thing that puzzles me is the color of your oil. In just over two weeks it turned from 0.5 to 6.5 (similar is when I do oil change on my VW Beetle TDI). This color, and the initial high cleanliness code after you filled new oil in the machine, suggest that you guys did not make a serious attempt to flush the system, if at all.
6. I don’t know if you guys ran compatibility test between new and in-service oils before you mixed them or filled the machine. Incompatibility may cause stripping of the additives, and caused such (and worst) rapid drop-off in RPVOT. For years we successfully used services of the Herguth Labs in “dodging the bullet”, by avoiding new oils that were tested and identified as being incompatible with our in-service oil. But now you, and everyone else, can use new, and first time ASTM assembled method for testing compatibility, ASTM D 7155-06, Standard Practice for Evaluating Compatibility of Mixtures of Turbine Lubricating Oils".
7. You did not post numbers for water in oil. I don’t know of what kind media you filter is made from, but a great performance we are getting from the cellulose type filters (like what the CCJensen and others offer). They are absorbent filters, and therefore, besides capturing particles, they take care of small amounts of water in oil, if it gets there. Of course, if there is a cooling water leak or other types of water ingression, that water should be dealt with a demoisturizer. However, if your Kleentek is not an absorbent type, you can always add an absorbent scrubber to it
8. According to the viscosity, your oil is at great shape. My suggestion would be to keep that Kleentek running 24/7. Your cleanliness will look better and better, and you might even enhance the color of oil. Also, it should be of no surprise to anyone to see RPVOT reading higher once the oil is cleaner. It has been noted in literature, and from my personal experience, a high load of contaminants can cause an early (premature) pressure drop during analysis, thus showing lower RPVOT than actually is. After filtering such oil, it showed better results (higher RPVOT). Also, keep an eye on AN and cleanliness (once in a month would be sufficient but you can do more often if that would give you piece of mind), and check RPVOT every 6 months until is stabilized. After that time, you can test it just once a year as long as AN stays fairly consistent. As a footnote, our AN warning limits for Group 1 turbine oils is at 0.5, and condemning limit at 0.70, providing that the initial AN (new oil) was 0.20 - 0.25.