90,000km/10 years since my last oil change, Esso XD-3 0W-30 oil.
High temperature Viscosity thickening is a well known feature of long drains. But just searching, I'm not able to find any good material, UOA's, etc., on what happens to the cold temperature viscosity of motor oil subjected to long drains.
XD-3 0W-30 is a Group IV PAO oil, with very high viscosity index basestocks. After 90,000k (56k miles), its probably safe to assume that any viscosity modifiers have been depleted. But in an oil with minimal viscosity modifiers due to high VI basestocks, would cold-temperature viscosity thickening be significant?
Any good papers? I see one, "ASTM STP621_S4 Cold Starting and Oil Pumpability —An Evaluation of New and Used Oils in Gasoline Engines", but its very old (~1980) and implies that a 'used' 10W-30 becomes a 20W-40 in their case. Not sure such logic is applicable to modern synthetics though which don't rely upon viscosity modifiers.
High temperature Viscosity thickening is a well known feature of long drains. But just searching, I'm not able to find any good material, UOA's, etc., on what happens to the cold temperature viscosity of motor oil subjected to long drains.
XD-3 0W-30 is a Group IV PAO oil, with very high viscosity index basestocks. After 90,000k (56k miles), its probably safe to assume that any viscosity modifiers have been depleted. But in an oil with minimal viscosity modifiers due to high VI basestocks, would cold-temperature viscosity thickening be significant?
Any good papers? I see one, "ASTM STP621_S4 Cold Starting and Oil Pumpability —An Evaluation of New and Used Oils in Gasoline Engines", but its very old (~1980) and implies that a 'used' 10W-30 becomes a 20W-40 in their case. Not sure such logic is applicable to modern synthetics though which don't rely upon viscosity modifiers.