The Rocle Test for Diesel and Bio-Diesel Fuel Lubricity

This bench test for lubricity of diesel fuels employs a crossed-axis roller on cylinder geometry. The roller on cylinder lubricity evaluator (ROCLE) yields a dimensionless lubricity number (LN) based on the ratio of wear area stress to Hertzian contact stress, all divided by the stable coefficient of friction.

Fuels yielding LN's greater than 1.0 are judged satisfactory. A range of lubricity numbers from 0.5 for kerosene to 1.7 for canola vegetable oil provides good tribological discrimination between various fluids. The addition of 2% canola methyl ester to low sulfur No.1 diesel produces equivalent lubricity to No.2 high sulfur diesel fuel.