Carbon Residue Studies of Polyphenyl Ethers and Ester-Based Lubricants Using a Microcarbon Residue Tester

A commercial microcarbon residue tester (MCRT) was used to measure the amount of carbon residue generated from ester-based lubricants with viscosities of 4 and 7.5 cSt and from the polyphenyl ethers 5P4E, 5P4E with an antioxidant additive, 4P3E and 3E2E. All of the lubricants showed significant volatilization at all temperatures with the polyphenyl ethers generally leaving residues which were less than 10 weight percent of the initial sample. An analysis of the weight percent residue as a function of location of the samples within the MCRT oven showed that a minimum of 6 sample vials distributed in either even or odd locations is needed to give reliable quantities of residue. Keywords: Lubricant degradation, Lubricant test, Polyphenyl ethers, Synthetic esters.