Yes, I used to work quite a bit with used oil analysis with electrical transformers and switchgear. I have absolutely total faith in the concept of oil analysis, and the ability of lubricants to 'last' for extended drains. Speaking of extended drains, many of the transformers were/are on their factory fills of oil 40, 50 years later, with filtering occurring once every 7 years or so, guided by a used oil analysis program.
Of course, instead of looking for 'wear metals', we looked at statistics such as moisture, dielectric strength, and dissolved gases such as hydrogen, acetylene, as well as oil decomposition components.
Recently a lot of the transformers have been fitted with real-time instrumentation that can be read from a distance through a computer modem. The oil we used was called 'Voltesso', manufactured in Sarnia, and delivered oil tanker at a time directly to our jobsites.
When oil disposal, especially PCB-laden oil disposal is such a huge concern, the only choice is to keep the oil in service as long as possible. So a used oil analysis, even at $500-$600 per sample, including labour and transportation, still remained a good investment.
