Low Temperature Rheological Studies of Hydrocarbon Base Lubricants

The low temperature rheological behavior of a number of lubricants was examined in the range of −12 to −37°C over a shear rate range of one to 1000 sec⁻¹. Results are presented for the following fluids: a waxy mineral oil, a synthetic hydrocarbon oil (poly-alpha olefin) and four oils each containing an olefin copol ymer (OCP) viscosity index improver with different additive packages. All samples were subjected to the same cooling history consisting of a 0.56°C/min cooling rate, followed by a one hour soak period before data was collected. These data demonstrate that waxy oils without VI improvers can show non-Newtonian and viscoelastic behavior similar to data at low temperatures for polymer-thickened oils in a non-waxy solvent. Combinations of wax and VI improver can show both shear thinning and shear thickening, as well as viscoelastic properties.