Metropolitan Diesel Bus Service Ranks Lubricating Oils Differently than Standardized Engine Tests

Six diesel engine crankcase oils, varying widely in additive type, were tested in diesel field service as well as several standardized laboratory diesel engine tests. The 150,000 mile field test was run in urban buses powered by a popular make of United States two-stroke cycle diesel engine. It was found that the best field deposit control was obtained with an oil containing a high level of succinimide (ashless dispersant). The parallel program showed that the laboratory engine tests did not predict relative field performance regarding ring sticking or sludge and varnish deposit control.