Anti-Rust Performance of Ash and Ashless Crankcase Oils in Short Trip Service

A short-trip rust test was conducted on both ash-containing and ashless oils, using both leaded and nonleaded fuels. Our findings show that ash-containing formulations are greatly superior, particularly during the last phase of this test. When one of the ashless formulations was used with nonleaded gasoline, a 3 average lifter rust number improvement was obtained over that found in leaded gasoline.

Pushrods and oil pump relief valves, in general, rusted very little, which is contrary to rusting found in Sequence Test IIC. Ash-containing oils allowed spotted patches of rust on the nontraveled areas of the hydraulic lifter plunger while ashless oils allowed an even rust on the total area of the traveled part. New lifters installed at the intermediate inspections had accumulated as much rust by the final inspection as those present from the beginning. This short-trip rust test in comparison to Sequence Test IIC has demonstrated an appreciation of ash-containing oils and a depreciation of ashless oils.