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A critical market driver for rear axle lubricants continues to be the improved fuel efficiency, which is related to improvements in power transfer efficiency. Power transfer efficiency improvements are achieved with a reduction in the kinematic viscosity (KV) of rear axle lubricants. General Motors (GM) recently reduced the recommended viscosity grade for their rear axle lubricants from the Society of Automotive Engineers standard (SAE) 75W-90 to SAE 75W-85. This reduction in viscosity continues to require the optimization of rear axle lubricants to ensure durability. Lubricants that form thick elastohydrodynamic (EHD) films and are shear stable even when lower kinematic viscosities are required. This work depicts how a rear axle lubricant was developed and improved with the proper selection of base oil and polymer. This newly developed SAE 75W-85 rear axle fluid was incorporated as factory fill in 2019 in T1 LDPU-GMC Sierra and Chevrolet Silverado 1500 series pickup trucks.

There is still a need in the industry for engine oils that have low viscosities to improve vehicle fuel efficiency but also protect engines from wear. Viscosity modifiers (VMs) are chief additives responsible for adjusting the viscometric characteristics of automotive lubricants. Most notably, VMs have a significant impact on a lubricant's viscosity-temperature relationship as indicated by viscosity index (VI), cold cranking simulator (CCS) viscosity, and high temperature high shear (HTHS) viscosity of engine oils. Functional copolymers bearing branched, linear, or anti-wear functionalities have been synthesized and evaluated for viscometric and wear protection performance. The resulting polymers improved tribofilm formation, shear stability and CCS viscosities. Indirect benefits including Noack improvement and trim oil reduction were observed.

There has been a trend in the automotive industry toward the use of lower viscosity engine oils as fuel economy requirements become more demanding across the globe. Lower viscosity fluids may improve fuel economy due to their improved pumpability, lower churning losses, and thinner lubricating films. However, there is one important caveat related to the use of these fluids: the amount of improvement, if any, is hardware design and application dependent. Standard industry fuel economy tests and engines with differing designs may show divergent responses when using lower viscosity engine oils, not always showing an improved fuel economy response. This paper summarizes the work conducted by the authors to demonstrate how and why the inconsistent results in fuel economy can occur with low viscosity oils.

Friction reduction in lubricated components through engine oil formulations has been investigated in the present work. Three different DI packages in combination with one friction modifier were blended in SAE 5 W-20 and SAE 0 W-16 viscosity grades. The friction performance of these oils was compared with GF-5 SAE 5 W-20 oil. A motored cranktrain assembly has been used to evaluate these, in which friction mean effective pressure (FMEP) as a function of engine speeds at different lubricant temperatures is measured. Results show that the choice of DI package plays a significant role in friction reduction. Results obtained from the mini-traction machine (MTM2) provide detailed information on traction coefficient in boundary, mixed and elastohydrodynamic (EHD) lubrication regimes. It has been shown that the results from the cranktrain rig are fairly consistent with those found in MTM2 tests for all the lubricants tested.

Mobile source emissions standards are becoming more stringent and particulate emissions from gasoline direct injection (GDI) engines represent a particular challenge. Gasoline particulate filter (GPF) is deemed as one possible technical solution for particulate emissions reduction. In this work, a study was conducted on eight formulations of lubricants to determine their effect on GDI engine particulate emissions and GPF performance. Accelerated ash loading tests were conducted on a 2.4L GDI engine with engine oil injection in gasoline fuel by 2%. The matrix of eight formulations was designed with changing levels of sulfated ash (SASH) level, Zinc dialkyldithiophosphates (ZDDP) level and detergent type. Comprehensive evaluations of particulates included mass, number, size distribution, composition, morphology and soot oxidation properties. GPF performance was assessed through filtration efficiency, back pressure and morphology.

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.

Improving vehicle fuel efficiency is a key market driver in the automotive industry. Typically lubricant chemists focus on reducing viscosity and friction to reduce parasitic energy losses in order to improve automotive fuel efficiency. However, in a transmission other factors may be more important. If an engine can operate at high torque levels the conversion of chemical energy in the fuel to mechanical energy is dramatically increased. However high torque levels in transmissions may cause NVH to occur. The proper combination of friction material and fluid can be used to address this issue. Friction in clutches is controlled by asperity friction and hydrodynamic friction. Asperity friction can be controlled with friction modifiers in the ATF. Hydrodynamic friction control is more complex because it involves the flow characteristics of friction materials and complex viscosity properties of the fluid.

Low speed pre-ignition (LSPI) is an undesirable combustion phenomenon that limits the fuel economy, drivability, emissions and durability performance of modern turbocharged engines. Because of the potential to catastrophically damage an engine after only a single pre-ignition event, the ability to reduce LSPI frequency has grown in importance over the last several years. This is evident in the significant increase in industry publications. It became apparent that certain engine oil components impact the frequency of LSPI events when evaluated in engine tests, notably calcium detergent, molybdenum and phosphorus. However, a close examination of the impact of other formulation additives is lacking. A systematic evaluation of the impact of the detergent package, including single-metal and bimetal detergent systems, ashless and ash-containing additives has been undertaken using a GM 2.0L Ecotec engine installed on a conventional engine dynamometer test stand.

Currently there is no axle test aimed specifically at bearing durability in automotive hypoid axles. Existing axle tests are primarily focused on gear distress and lubricant protection of gears. In light of the new test information showing axle bearing distress, there is a need to develop a new bearing durability test for automotive and truck axle lubricants. To fulfill this need, a new bearing durability test has been developed to better assess lubricant requirements for rolling element bearing durability. Although the final test of an axle lubricant is in a driven automobile or truck, an effective screening test based on actual light duty truck conditions can be used to accelerate lubricant development to enhance bearing performance in hypoid axles. This new test simulates actual road durability tests in the lab. A specific load cycle which retains the critical road test loading conditions reduces test time and helps speed up lubricant development.

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.

Biodiesel fuel is a promising new renewable, alternate fuel source. However, its effect on diesel engine oil lubrication is largely untested at present. There is some indication that the use of biodiesel fuel can degrade diesel engine oil performance to such an extent that shortening of oil drain intervals is required. Oil which is fuel-diluted with biodiesel, which is known to contain unsaturated hydrocarbon bonds, would be expected to be more prone to oxidation. Current diesel engines designed to meet environmental standards tend to introduce more soot into the crankcase oil. The new diesel engine oils for use with biodiesel fuel must be capable of dispersing soot to minimize soot-induced viscosity increase of the oil and prevent engine wear. Oils will also need improved oxidation and corrosion inhibition. To examine soot-handling, ASTM D 7156 Mack T-11 engine test results with 20 wt% soy methyl ester in ultra-low sulfur diesel fuel (B20) were employed.

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.

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-use vehicle regional inspection and maintenance (I/M) programs in the United States (US) and Canada generate a tremendous volume of data that provides a means for evaluating vehicle emissions compliance in actual consumer use. In this study, IM240 test data for several 1996 to 2001 vehicle models are analyzed from different regional programs in the US and Canada to confirm the suitability of using these data for evaluation of vehicles equipped with advanced emission control technology and to examine the various potential factors responsible for emissions noncompliance. Relative comparisons between US and Canadian program data are made for vehicle models used in the Alliance of Automobile Manufacturers (AAM) MMT® Test Program to examine the potential impact of differences in fuel properties on consumer experience and vehicle compliance.

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.