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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.

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 single cylinder engine was used to collect engine combustion chamber deposits insitu, and to investigate the influence of fuel composition on combustion chamber deposit formation. High-boiling aromatic compounds were found to contribute greatly to deposit formation, while olefinic compounds did not show any significant deposit-forming tendencies. In a low surface temperature regime, deposit formation increased with boiling point of aromatic dopants added to the base fuel. Various analytical techniques (FTIR, GC/MS, EPMA, SEM) were utilized to characterize carbonaceous deposits in an early stage of formation. Oxidized hydrocarbon species (ketones, carboxylic acids, lactones, esters), metal carboxylates, and decomposition products of oil additives were found to be major building blocks of deposits. The oxidized hydrocarbon species formed in a preflame region are condensed/adsorbed on a relatively cold surface to form combustion chamber deposits.

A single-cylinder engine was used to study the effect of engine operating parameters on the early stage of deposit formation (first 8 hours). Deposit samples were collected from the engine cylinder using removable sampling probes. Among the engine operating parameters studied, coolant temperature had the greatest influence on deposit formation. Equivalence ratio of the air-fuel mixture was also important. Other variables such as compression ratio and intake air temperature had minimal effects. Investigations using a temperature controlled probe revealed that surface temperature is a dominant factor in the deposit forming process. Within a temperature range from 98°C to 256°C, there is an inverse relationship between the amount of deposit accumulated and the surface temperature. Extrapolating the experimental data showed that the critical surface temperature for deposit formation is near 310°C, above which no deposit is expected to form.

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.