A Bench Scale Engine Test for Shear Stability of Multigrade Engine Oils

A procedure is described which employs an air-cooled, 4-cycle, single-cylinder engine of the type often found on lawn and garden equipment, driven by an electric motor at 3100 rpm.

The equipment is simple, inexpensive, and requires a modest volume of sample. Results compare favorably with the shear stability tests of a series of 13 oils prepared and field-tested in a 78 vehicle fleet by Subsection B-1 of ASTM Division VII of Committee D 2. The degree of correlation is comparable to that observed in several tests conducted in full size laboratory engine stands, and superior to that recently reported for a variety of non-engine bench tests (pump rigs, sonic oscillator, dispersion mill).

Viscosity losses are also reported for a variety of commercial 10W-40 grade service station engine oils, when tested by this procedure.