As a result of diesel engine failures being experienced in the field with “approved” engine oils, an extensive truck field test has been run with over 40 different oil formulations ranging in quality from CA to CD/SE/1% ash in four major types of diesel engines.
Results show that fire-ring sticking is the major problem with a trunk piston 2-cycle engine and this appears to be related to the additive composition rather than the oil classification level. An examination of the groove deposits shows that ring sticking is the result of rapid ash build-up in the fire-ring groove under severe operating conditions. A crosshead piston/keystone ring combination has eliminated the ring sticking problem with this engine even though the two piston types build up similar deposit levels. A 10W/30 multigrade oil gives excellent performance in the crosshead piston 2-cycle engine.
A major type of four-cycle engine gives satisfactory performance with oils ranging in quality from CC/SC to CD/SE, although the higher dispersant SE quality oils do give lower groove fill and cleaner overall engine condition. The 10W/30 multigrade oil gives excellent performance in this engine and in fact shows a definite benefit with regard to bearing wear.
Two further types of four-cycle engines have been shown to give excellent performance with a Universal oil and with a 10W/30 multigrade oil using 16-18M mile oil change intervals.