The design of fuel efficient automotive hypoid gear lubricants

Abstract

Synthesised lubricant base stocks and the performance additives used in hypoid gear lubricants can both be chemically designed to give improved hypoid gear eficiency and, therefore, better vehicle fuel economy than provided by conventional lubricantsIn this paper, the authors review, relative to a widely used SAE 90 grade mineral oil-based lubricant, the changes in gear efJiciency which have been documented using certain classes of synthesised lubricants. These advantages are described in terms of (a) EPA City and Highway Cycle eflciencies, (b) absolute data over a wide temperature range under four selected speedtorque combinations, and (c) absolute changes in ineficiency compared to the mineral oil product.Newtonian and non-Newtonianfluids have been studied. The bulk oil temperature at which a specific lubricant gives maximum eflciency is dependent on both gear operating conditions and on the chemical composition of the lubricant. 140 140 I 0 Bulk oil temperature, 'C JSL 11-1 I0 0265-6582 $7.00 + $2.50