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Deposit formation within turbocharger compressor housings can lead to compressor efficiency degradation. This loss of turbo efficiency may degrade fuel economy and increase CO2 and NOx emissions. To understand the role that engine oil composition and formulation play in deposit formation, five different lubricants were run in a fired engine test while monitoring turbocharger compressor efficiency over time. Base stock group, additive package, and viscosity modifier treat rate were varied in the lubricants tested. After each test was completed the turbocharger compressor cover and back plate deposits were characterized. A laboratory oil mist coking rig has also been constructed, which generated deposits having the same characteristics as those from the engine tests. By analyzing results from both lab and engine tests, correlations between deposit characteristics and their effect on compressor efficiency were observed.

The recirculation of gases from the crankcase and valvetrain can potentially lead to the entrainment of lubricant in the form of aerosols or mists. As boost pressures increase, the blow-by flow through both the crankcase and the valve cover increases. The resulting lubricant can then become part of the intake charge, potentially leading to fouling of intake components such as the intercooler and the turbocharger. The entrained aerosol which can contain the lubricant and soot may or may not have the same composition as the bulk lubricant. The complex aerodynamic processes that lead to entrainment can strip out heavy components or volatilize light components. Similarly, the physical size and numbers of aerosol particles can be dependent upon the lubricant formulation and engine speed and load. For instance, high rpm and load may increase not only the flow of gases but the amount of lubricant aerosol.

Biodiesel-blended fuel is increasingly becoming available for diesel engines. Due to seasonal and economic factors, biodiesel available in filling stations can be sourced from varying feedstocks. Moreover, biodiesel may not contain the minimum oxidative stability required by the time it is used by the automotive consumer. With fuel dilution of engine oil accelerated by post-injection of fuel for regeneration of diesel particulate filters, it is necessary to investigate whether different biodiesel feedstocks or stabilities can affect engine oil properties. In this work, SAE 15W-40 CJ-4 is diluted with B20 fuel, where the B20 was prepared with soy methyl ester (SME) B100 with high Rancimat oxidative stability, SME B100 with low oxidative stability, and lard methyl ester (LME). The oils were then subjected to laboratory aging simulating severe drive cycles. At intermediate aging times, samples were obtained and additional B20 was added to simulate on-going fuel dilution.

High concentrations of diesel fuel can accumulate in the engine oil, especially in vehicles equipped with diesel particle filters. Fuel dilution can decrease the viscosity of engine oil, reducing its film thickness. Higher concentrations of fuel are believed to accumulate in oil with biodiesel than with diesel fuel because biodiesel has a higher boiling temperature range, allowing it to persist in the sump. Numerous countries are taking actions to promote the use of biodiesel. The growing interest for biodiesel has been driven by a desire for energy independence (domestically produced), the increasing cost of petroleum-derived fuels, and an interest in reducing greenhouse gas emissions. Biodiesel can affect engine lubrication (through fuel dilution), as its physical and chemical properties are significantly different from those of petrodiesel. Many risks associated with excessive biodiesel dilution have been identified, yet its actual impact has not been well quantified.

Engine oils are subjected to a series of industry standard engine dynamometer tests to measure their wear protection capability, sludge and varnish formation tendencies, and fuel efficiency among several other performance attributes before they are approved for use in customer engines. However, these performance attributes are measured at the end of tests and therefore, do not provide any information on how the properties have changed during the tests. In one of our previous studies it was observed that engine oil samples collected from fleet vehicles after 12,000 mile drain interval showed 10-15 % lower friction and more importantly, an order of magnitude lower wear rate than those of fresh oils. It was also observed that the composition of the tribochemical films formed was quite different on the surface tested with the drain oils from those formed with fresh oils.

Phosphorus is known to reduce effectiveness of the three-way catalysts (TWC) commonly used by automotive OEMs. This phenomenon is referred to as catalyst deactivation. The process occurs as zinc dialkyldithiophosphate (ZDDP) decomposes in an engine creating many phosphorus species, which eventually interact with the active sites of exhaust catalysts. This phosphorous comes from both oil consumption and volatilization. Novel low-volatility ZDDP is designed in such a way that the amounts of volatile phosphorus species are significantly reduced while their antiwear and antioxidant performances are maintained. A recent field trial conducted in New York City taxi cabs provided two sets of “aged” catalysts that had been exposed to GF-4-type formulations. The trial compared fluids formulated with conventional and low-volatility ZDDPs. Results of field test examination were reported in an earlier paper (1).

Engine oils contain additives that provide wear protection to prolong engine life. In a previous study using direct acting mechanical bucket valve train components, we found that aged oil provided better wear protection and friction reduction under certain circumstances. To understand this effect further, friction and wear performance of fresh and laboratory-aged oils with 0.1% phosphorus was studied with ball-on-flat and cylinder-on-flat rigs. Test durations were chosen according to the electrical contact resistance (ECR) values observed between the contacting surfaces. Anti-wear films were characterized primarily by UV and visible Raman spectroscopy, and results were corroborated by Auger electron and infrared spectroscopies. The greatest compositional differences occurred between films formed by fresh and aged oils. The degree of ECR response or the length of oil aging generally did not affect the type of component observed in the films.

Catalyst durability is a major concern in automotive exhaust gas treatment, and can be affected by chemical and thermal history. In this work, applications of in situ UV and visible Raman spectroscopy to a variety of catalyst deactivation issues are demonstrated: a) identification and characterization of CePO4 in three-way catalysts. CePO4 forms from the interaction of phosphorus in engine oil additives with the catalyst washcoat. It affects oxygen storage and decreases catalyst conversion efficiency. b) thermal deactivation in Pd/ceria-zirconia catalysts. A compressive strain on palladium oxide as indicated by its Raman shift can serve as a diagnostic for a thermally-deactivated catalyst and thus the unavailability of the Pd for catalysis. c) sulfur poisoning, thermal deactivation and BaCO3 formation in lean NOx traps (LNT).

Phosphorus contamination from engine oil additives has been associated with reduced performance of vehicle-aged exhaust gas catalysts. Identifying phosphorus species on aged catalysts is important for understanding the reasons for catalytic performance degradation. However, phosphorus is present only in small quantities, which makes its detection with bulk analytical techniques difficult. Raman microscopy probes small regions (a few microns in diameter) of a sample, and can detect both crystalline and amorphous materials. It is thus ideal for characterizing phosphates that may have limited distribution in a catalyst. However, suitable Raman spectra for mixed-metal phosphates that might be expected to be present in contaminated catalysts are not generally available.