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There has been a global technology convergence by engine manufacturers as they strive to meet or exceed the ever-increasing fuel economy mandates that are intended to mitigate the trend in global warming associated with CO2 emissions. While turbocharging and direct-injection gasoline technologies are not new, when combined they create the opportunity for substantial increase in power output at lower engine speeds. Higher output at lower engine speeds is inherently more efficient, and this leads engine designers in the direction of overall smaller engines. Lubricants optimized for older engines may not have the expected level of durability with more operating time being spent at higher specific output levels. Additionally, a phenomenon that is called low-speed pre-ignition has become more prevalent with these engines.

This paper provides an overview of driveline fluids, in particular automatic transmission fluids (ATFs), and is intended to be a general reference for those working with such fluids. Included are an introduction to driveline fluids, highlighting what sets them apart from other lubricants, a history of ATF development, a description of key physical ATF properties and a comparison of ATF fluid specifications. Also included are descriptions of the chemical composition of such fluids and the commonly used basestocks. A section is included on how to evaluate used driveline oils, describing common test methods and some comments on interpreting the test results. Finally the future direction of driveline fluid development is discussed. A glossary of terms is included at the end.

In the next ILSAC passenger car motor oil specification the Sequence IIIG engine test, as well as two versions of the Thermo-Oxidation Engine Oil Simulation Test (TEOST) have been proposed as tests to determine the ability of crankcase oils to control engine deposits. The Sequence IIIG engine test and the TEOST MHT test are designed to assess the ability of lubricants to control piston deposits and the TEOST 33 test is designed to assess the ability of lubricants to control turbocharger deposits. We have previously characterized the chemical composition of Sequence IIIG piston deposits using thermogravimetric, infrared and SEM/EDS analyses. Sequence IIIG piston deposits contain a significant amount of carbonaceous material and the carbonaceous material is more prevalent on sections of the pistons that should encounter higher temperatures. Furthermore, the carbonaceous material appears to be a deposit formed by the Sequence IIIG fuel.

An engine test has been developed to assess the impact of volatile phosphorus from passenger car engine oils on catalytic converter efficiency. The ten-day, steady-state, catalyst aging test was established to promote the production and consumption of volatile phosphorus species contained in crankcase vapors that are evacuated and combusted via the PCV system. A system for sampling, analyzing and identifying crankcase vapors led to a greater understanding of the phosphorus-based poisoning mechanism. Catalytic converter conversion efficiency was assessed through an engine-based system that swept catalyst inlet temperature from low to high while using a constant flow of controlled exhaust gas. The test results indicate correct ranking of field-tested oils that have catalyst poisoning data.

Different mechanical components in a vehicle can be made from different steel alloys with various surface treatments or coatings. Lubricant technology is needed to prevent wear and control friction on all of these different surfaces. Phosphorus compounds are the key additives that are used to control wear and they do this by forming tribofilms on surfaces. It has been shown that different operating conditions (pressures and sliding conditions) can influence the formation of tribofilms formed by different anti-wear additives. The effect of surface metallurgy and morphology on tribofilm formation is described in this paper. Our results show that additive technology can form proper tribofilms on various surfaces and the right combination of additives can be found for current and future surfaces.

Countries from every region in the world have set aggressive fuel economy targets to reduce greenhouse gas emissions. To meet these requirements, automakers are using combinations of technologies throughout the vehicle drivetrain to improve efficiency. One of the most efficient types of gasoline engine technologies is the turbocharged gasoline direct injection (TGDI) engine. The market share of TGDI engines within North America and globally has been steadily increasing since 2008. TGDI engines can operate at higher temperature and under higher loads. As a result, original equipment manufacturers (OEMs) have introduced additional engine tests to regional and OEM engine oil specifications to ensure performance of TGDI engines is maintained. One such engine test, the General Motors turbocharger coking (GMTC) test (originally referred to as the GM Turbo Charger Deposit Test), evaluates the potential of engine oil to protect turbochargers from deposit build-up.

Sliding contact between friction surfaces occurs in numerous torque transfer elements: torque converter clutches, shifting clutches, launch or starting clutches, limited slip differential clutches, and in the meshing of gear teeth under load. The total temperature in a friction interface is the sum of the equilibrium temperature with no sliding and a transient temperature rise, the flash temperature, caused by the work done while sliding. In a wet shifting clutch the equilibrium temperature is typically the bulk oil temperature and the flash temperature is the temperature rise during clutch engagement. The flash temperature is an important factor in the performance and durability of a clutch since it affects such things as the reactivity of the sliding surfaces and lubricant constituents (e.g., oxidation) and thermal stress in the components. Knowing how high the flash temperature becomes is valuable for the formulation of ATF, gear oil, engine oil and other lubricants.

Deposit formation is an issue of great significance in a broad range of applications where lubricants are exposed to high temperatures. Lube varnish causes valve-sticking, bearing failure and filter blockage which can lead to considerable equipment downtime and high maintenance costs. Recently this has become a pressing issue in the stationary power generation industry. In order to investigate the chemistry leading to varnish, three samples of varnish-coated components from the lube/hydraulic systems of gas turbines from the field were obtained, along with information on the commercially available formulated oils which were used. Samples of these three fresh oils were analysed by a variety of chromatographic and spectroscopic techniques, which confirmed chemical identity of aminic and/or phenolic antioxidants, corrosion inhibitors and antiwear components. The varnish-coated turbine components were also investigated by these methods.

Previous research to understand the mechanism for piston deposit formation in the Sequence IIIG engine test has focused on characterizing the piston deposits. These studies concluded that, in addition to lubricant derived materials, Sequence IIIG piston deposits contain a significant amount of fuel-derived carbonaceous material. The presence of fuel degradation by-products in Sequence IIIG deposits shows that blow-by is a significant contributor to deposit formation. However, blow-by can either assist in the degradation of the lubricant or can simply be a source for organic material which can be incorporated into the deposits. Therefore, a series of modified Sequence IIIG engine tests were conducted to better determine the effect of blow-by on deposit formation. In these studies deposit formation on different parts of the piston assembly were examined since different parts of the piston assembly are exposed to different amounts of blow-by.