Search Results

Oil formulation has been found to be a significant factor in high rates of 6.2 L diesel engine, roller hydraulic valve lifter wear that occurred in field service with some commercial engine oils. This was confirmed through engine-dynamometer testing. A correlation has been established between engine-dynamometer wear test results and those obtained in laboratory four-ball wear tests conducted with used engine oil. The effects of dispersant level, viscosity, sulfonate metal type, sulfonate total-base-number, zinc dialkyl dithiophosphate (ZDTP) type, and ZDTP concentration on wear were systematically investigated. Wear increased with increasing soot concentration in the oil, and decreased with increasing sulfur concentration, both in the oil and on the metal surface. Wear also decreased with increasing dispersant concentration. The remaining oil variables had minimal effects on wear within the ranges studied.

A laboratory test procedure was developed, and used to evaluate the deposit-forming tendencies of liquid fuels on a metal surface, and to identify deposit precursors in fuel. The impetus for this work was deposit formation in multiport fuel injection(MPFI) systems. Results from our laboratory test correlated well with those from engine dynamometer tests. Deposit formation is shown to be caused by the oxidation, condensation, and precipitation of unstable hydrocarbon species in the fuel. The immediate precursors for deposit formation were determined, based on liquid chromatographic separation and GC/MS analysis, to be oxygenated hydrocarbons included in the fuel.

A laboratory Ball Rust Test (BRT) has been jointly developed by General Motors and Ethyl Corporation to replace the current Sequence IID engine test, and standard test procedures have been established to assess the rust/corrosion protection ability of experimental and commercial oils. Under the optimum test conditions developed, BRT data on eight industry reference and eighteen industry supplied oils showed a reasonable correlation with Sequence IID average rust test results. The capability of the BRT for differentiating oil quality was further demonstrated by evaluating 132 commercial oils obtained from around the world: oils with insufficient protection, such as those with API performance ratings of SA to SE, performed poorly in the BRT; oils with API ratings of SF, SG, and SH performed well in the test. The BRT will be made available to ASTM for development of a precision statement and for inclusion in future engine oil performance specifications.