Quincy screw air compressor:
originally used Quin-Syn POA V.G.46, operating manual states to change oil between 4000-8000 hours depending on lube oil analysis
one limit is to keep the acid number less than 1
several years ago the oil was changed from Quin-Syn V.G. 46 to Anderol 497 V.G. 68 diester synthetic, not sure why they changed, but the Anderol TAN will be greater than 1 in a month or two. Each compressor takes nearly a barrel of oil (approx $2400 per barrel). We normally do an oil change each year (approx. 8000 hours) and the TAN approaches 3, new oil TAN is almost zero.
My question is, should we be changing oil based on TAN, if so at what limit.
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