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Corrosive wear of non-ferrous engine components by lubricants is a concern of all major heavy duty diesel engine manufacturers since warranty on key engine components has been extended to 500,000 miles. Several commercial lubricants have been linked to premature cam and rod bearing failures induced by corrosion in certain fleets. Although the overall failure rate is low, specific fleets have experienced significantly higher failure rates due to the lubricants used. These failures usually occur at high mileages but less than 500,000 miles. This kind of slow corrosion easily escapes detection of engine tests contained in current oil specifications, and it represents a serious issue in long term warranty cost to diesel engine manufacturers. A comprehensive fleet database has been established to identify the most corrosive lubricants. These lubricants have served as reference oils to develop a corrosion bench test.

An engine rig test and a scuffing BOCLE test have been used to investigate the lubricity of low sulfur diesel fuels and its relationship with unit injector wear in heavy duty diesel engines. The rig test effectively ranks 11 selected fuels/fluids according to their actual performance. The scuffing BOCLE test correlates with the rig test by showing the same ranking capability, and it is easy to perform. A similar correlation has been established using ISO reference fuels. The scuffing BOCLE test has been used to study 37 fuels randomly sampled from the field. The data shows that there is indeed a reduction in lubricity of low sulfur fuels. The variation in lubricity of low sulfur fuels is also much greater than high sulfur fuels. Data in this study shows that transition from good to poor lubricity usually occurs between 2500 to 3000 grams in the scuffing BOCLE.

Reports of disabling diesel engine seal failures which accompanied the introduction of low sulfur diesel fuel in October '93 prompted an in-depth survey of diesel fuel chemical and physical properties. The purpose of the survey was to anticipate other possible problems which might arise with the newly introduced low sulfur fuels. The survey will produce a database containing over 1000 number 2 diesel fuels from various parts of the US. About 75% of the samples tested were on-highway low sulfur diesel fuels. Samples analyzed were from the D-A Lubricant Company, Cummins customers failures (truck fleets of various sizes), and a number of retail fueling stations. Properties under investigation are % Sulfur, Cloud/Pour Points, Viscosity, API Gravity, TAN/TBN, Boiling Range, Aromatics content, Heat Content, Lubricity, and Peroxide number.

Tests were conducted with several production diesel engines and one prototype low-emission diesel engine to determine the effect of fuel properties on exhaust emissions and engine performance. Fuel cetane number was found to be the most significant fuel property; low cetane fuels resulted in higher hydrocarbons and oxides of nitrogen and increased noise. Conversely, higher cetane fuels produced lower emissions and noise, and also improved engine starting characteristics. The degree of these effects was influenced by engine configuration. Although engine design changes can result in substantial emissions reduction, fuel properties can also influence achieveable levels.

Reports of disabling elastomer seal failures across a wide range of diesel equipment, which accompanied the introduction of low sulfur diesel fuel in October '93 prompted an in-depth investigation of low sulfur diesel fuel chemical speciation. The objective of this work was to gain a better understanding of how low sulfur fuels had changed to cause this problem. Mass Spectroscopy (MS) and seal swell data were obtained on a broad geographical sampling of low sulfur diesel fuels obtained during the 4th quarter of '93. Previously available high sulfur (0.25%) data were available for comparison. Elastomer seal swell data were obtained in pure component blends and also in fuels which had caused field failures. Using these data it was possible to determine which fuel components or lack thereof may contribute most heavily to seal swell failures. Further, compression set data were obtained for a number of commonly used fuel system elastomers in a fuel which caused field problems.