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.

esters will show a higher TAN much faster than a PAO that said pehaps check with them on a recomendation bye the way other brands are in the $30 gal range and will run as well or better than anderol look around.
bruce

esters can go 2-3 TAN and be OK
bruce

Thank you bruce381
I will change the oil at 8000 hours as long as the TAN is <3 and the rest of the oil analysis looks O.K.

even with a higher than you would think TAN most esters will solubilize any sludge formation and still be Ok do what you sugested and keep an eye on it.
bruce