I am using Tivela S 460 in a worm gear application. I have had one of two things happen to the oil. Either the oil is contaminated with product, organic, or the oil is contaminated with another oil. I see no sludge in the oil, yet it is almost coffee colored and plugging the filters.

milky look is usally due to water but also could be contamination from say a PAG type gear oil good idea to change out.
bruce

I am not familiar with Tivela S, but from an on-line source (patent dealing with PAG lubricated robots)

According to an embodiment of the invention said polyglycol- based lubricant is a Tivela® oil, available from Shell. Tivela S oils are high performance, anti-wear, synthetic polyalkylene glycol-based oils with an extremely high viscosity index. They are resistant to the formation of harmful oxidation products, which results in a cleaner oil.

So Tivela are PAG oils. Was there a different oil in the gear application - mineral oil/preservative- prior to the Tivela - additives insoluble in PAG - insoluble basestock should pass through filter?

Can you check for wear metals or dilute used oil with a polar solvent (solvent dissolves new Tivela) If diluted oil hazy/cloudy pass through fine filtration/centrifuge (settle over weekend) to isolate plugging species

If its a PAG i would look toward contamination from a "mineral" oil they are perhaps not miscible in each other that may show up as a milky goo cloging things. Some time oil transfer pumps, meters etc are NOT cleaned of prevoius oils and you may have that as a contamination sourse.
bruce

Tivela is a PAG oil as previously stated, one of the major side effects of PAG oils is they are effectively paint strippers. Do not put them into gearcases which have any type of internal paint or coating as they will remove it. Also as others have said they are not miscible with normal mineral oils or PAO synthetics so if the changeover procedure prior to putting the oil in service was not strictly adhered to then a problem may develope.

As a former Shell guy would agree with the last two posts, one further thing to do.
Take a sample and leave to settle,preferably in a warm environment, as PAG has a SG of ~1, any mineral oil/PAO will ries to the surface and contents will hopefully settle into 2 layers.(top min. oil lower PAG
PAG OK with some paints.
Water check also advised, Water soluble in PAG