Search Results

This paper presents computer simulations of HTHS capillary viscometer dynamics for non-newtonian oils. The main objectives are to promote a deeper understanding of HTHS capillary viscometry and to support, on a theoretical basis, the empirical procedural modifications endorsed by ASTM. These modifications are explained by the fundamental behavior of non-newtonian fluids in capillaries. Current ASTM HTHS viscosity measurements use instruments in one of two categories: rotational or capillary. An initial discrepancy between the results from these two geometries motivated ASTM to re-examine the basics of HTHS viscometry, and resulted in modifications to the capillary procedures. These modifications were supported by limited experimental data suggesting the elimination of the previous discrepancy. This paper explains the physical cause of the discrepancy and the success of the procedural modification.

Two programs were conducted to study the relationships between engine oil rheology and crankshaft bearing wear. A Chassis Dynamometer test of four oils in four cars was used to explore and define the key variables affecting bearing wear. These results were used to design a Field Test of nine oils in 45 taxicabs in New York City. The test oils (SAE OW-20 to 20W-20) were formulated to measure the effects of viscosity, viscosity index improver, and detergent inhibitor package. Bearing wear tended to be either low and unremarkable or very high, particularly in the thrust bearings. Oil performance was best expressed as the frequency of excessive wear, rather than by quantitative wear measurement. There were many instances of very high wear in cabs operated with the lowest viscosity oils but none in cabs with higher viscosity oils.