Mineral base oils, 3 polyol polyester oils, and 2 polyalkylene glycol oils, viz., pentaerythritol tetrahexanoate (1), pentaerythritol tetra-2-methylpentanoate (11) and pentaerythritol tetraisovalerate (111), kinematic viscosity (40 degrees C) 19.4, 22.3 and 41 mm(2)/s, resp., and their educts (pentaerythritol, hexanoic acid, etc.) were examd. by the CEC L-33-A-93 procedure to det. (a) primary biodegradability (diisotridecyl adipate (IV) as ref.) and by the modified ISO 9888 (Zahn-Wellen's method, OECD 302B) and ISO 14593 (OECD 301B) methods (ethylene glycol as ref.) to det. (b) ultimate biodegradability. (a. b) 1, 90, 71; 11, 42; 58; III, 88, 78; and IV, 90, 48016; for mineral and vegetable oils by OECD 301B: (b) 4248 and 72-80%, resp. In the CEC test, abiotic degradation made the a-data high; the b-data were the more reliable. For polyol polyesters, the CEC is only partly useful. Polyoxyethylene diol and polyoxypropylene diol, 41 and 33 mm(2)/s (M = 350 and 450), gave: (b) 85 and 62% (ISO 9888) and 78 and 63% (ISO 14593), resp. For mixts. of water-insol. compds. the most useful is the 14593. Its modification (CONCAWE OECD 302D) enables the inherent slow biodegradability of oils to be detd.. Principles of biodegradation, standardized test methods for org. compds., particularly lubricants, were reviewed. 44 refs.