Cam and Lifter Wear as Affected by Engine Oil ZDP Concentration and Type 770087
The recent increase in excessive camshaft and lifter wear after extended service has shown that some SE-quality engine oils do not provide adequate protection.
To determine the effects of oil additives on wear, controlled tests were run using 1972-1974 model cars, unleaded gasoline, and either SE commercial products or experimental formulations. Field experience with 1970-1975 model trucks, leaded gasoline, and SE/CC or SE/CD oils was also investigated.
With some commercial oils, in both controlled tests and field experience, excessive wear sometimes occurred after extended service, even with recommended oil-change intervals. Generally, protection from excessive wear was best provided by those oils containing pre-dominantly alkyl ZDP (zinc dithiophosphate) antiwear additive instead of aryl ZDP. These results show that a laboratory engine test is needed to evaluate the long-term wear protection of engine oils.