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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.

A unique silver/alumina selective catalytic reduction (SCR) catalyst which used hydrocarbons (HC-SCR) to reduce NOx emissions was investigated. Diesel fuel or ethanol were used as the reductants to evaluate catalyst performance. Several full size 5.0L monolith 2.0 and 3.0 wt.% Ag2O-Al2O3 catalysts were created. Testing was conducted using a 6.6L Duramax turbocharged heavy duty diesel engine. Dynamometer testing on the heavy duty FTP and SET 13 transient test cycles was conducted. The NOx conversion efficiency was evaluated as a function of catalyst volume, inlet cone angle, hydrocarbon to NOx ratio (HC:NOx), and space velocity. Oxygen effects on the NOx reaction and the HC slip past the HC-SCR catalyst were also determined. An FTIR was used to evaluate unregulated emissions. Testing on the heavy duty FTP and SET 13 test cycles, with diesel fuel as the reductant, resulted in a 60% and 65% NOx conversion reduction respectively.

The two most common NOx reducing technologies, in an oxygen abundant exhaust stream, are urea selective catalytic reduction urea-SCR and lean NOx trap (LNT) catalysts. Each technology has advantages and disadvantages. Another selective catalytic reduction (SCR) catalyst that uses hydrocarbons (HC-SCR), specifically diesel fuel, as the reductant to reduce NOx emissions was investigated. This catalyst is a result of a high throughput discovery project and conducted in cooperation with BASF, Accelrys and funded by the Department of Energy (DOE.) Several full size 5.0L monolith catalysts were made and evaluated using a V6 turbo charged diesel engine connected to a dynamometer running light-duty transient test cycles. The NOx efficiency on the HWYFET and US06 tests were measured to be 92% and 76% respectively. The FTP was 60% on a weighted basis.

Minimum bearing oil film thickness (MBOFT) was measured in both a main and a connecting-rod bearing of a production V-6 engine using the total capacitance method (TCM). MBOFT was measured at 1500 rpm and at three different engine loads (64, 128, and 192 Nm). The oil sump temperature was controlled at 100°C. Five engine oils were tested (SAE grades 5W-20, 20W-20, 5W-30, 10W-30, and 20W-50) with emphasis given to the SAE 5W-30 and 10W-30 oils. MBOFT was also calculated using a computer code. The absolute minimum of the MBOFT (MBOFTmin, closest approach between the journal and the bearing) increased with increasing values of a Sommerfeld parameter (viscosity/load) and this dependence was similar in both the main and the connecting-rod bearings. But, for the main bearing the MBOFTmin values showed a higher dependence on the Sommerfeld parameter than those for the connecting-rod bearing. Similar results were obtained with the theoretical calculations of the MBOFT_min values.