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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.

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.

It is generally accepted that significant gains in fuel economy can be accomplished by reducing friction between the moving surfaces in key engine components (e.g. valvetrain, piston, crankshaft). This paper provides an overview of how specific tribological/rheological properties (e.g. viscosity, volatility, friction coefficient, film thickness, wear volume) can be considered in the design of fuel efficient crankcase engine lubricants that promote high wear resistance. Here, an example in how base stock, viscosity modifier (VM) and friction modifier (FM) can impact the surface friction is given. Friction and wear measurements from bench level lubrication characterization test methods mainly, high frequency reciprocating rig (HFRR) and mini-traction machine (MTM), are presented.

The oxidation process and mechanism of an 80W-90 axle/gear oil was studied using the laboratory modified Universal Oxidation Test (ASTM D4871). It provides useful information to better understand the oxidation behavior of a typical sulfur-phosphorus based GL-5 gear lubricant. Most importantly, the laboratory bench test provides helpful information regarding how hot is hot for the axle temperatures likely encountered during the actual field-trial driving. The testing result shows that the temperature of an axle lubricant is a decisive factor during the oxidation process. At the temperatures higher than 163°C, the viscosity and TAN increase very rapidly within a short period of time. The single FT-IR absorbance at 1715 cm-1 provides helpful complementary information to the oxidation process of the axle lubricants. The general trend of FT-IR agrees with both the viscosity change and TAN change of oxidized axle/gear lubricant.

Future vehicle emission regulations both in the US and Europe will require maintaining catalyst efficiency for longer mileage intervals. In order to achieve this requirement, chemical restrictions are being placed on elements in engine oil that can poison catalysts. Most of phosphorus and a significant amount of sulfur in current engine oils come from zinc dialkyldithiophosphates, ZDDPs, which are a class of cost-effective multifunctional additives providing wear, oxidation and corrosion protection. Reducing ZDDP concentrations raises oxidation and wear concerns. The overall purpose of this research is to look at the antioxidation and antiwear capability of low phosphorus engine oils containing 0.05 wt% phosphorus and the potential of engine oils formulated without phosphorus. In addition to fresh oils, used oils drained from fleet vehicles were also analyzed and evaluated.

The overall purpose of this research is to determine the antiwear capability of low phosphorus engine oils containing 0.05 wt% phosphorus. The antiwear performance of 0.05 wt% phosphorus engine oils was evaluated using a laboratory valvetrain bench test rig coupled with an on-line wear measurement technique and a high frequency reciprocating rig (HFRR). Low phosphorus engine oils were compared with GF-3 engine oils containing 0.1 wt% phosphorus. In addition to fresh oils, long drain used oils from fleet vehicles were also analyzed and investigated. This information is important to develop engine oil formulations to meet the latest government emission and fuel economy requirements. The results indicate that by appropriately selecting and balancing supplemental antiwear and/or antioxidation additives the wear loss due to the reduction of zinc dialkyldithiophosphate (ZDDP) may be compensated or even reduced.