DeBlase, F., Corbo, F., and Migdal, C., "Expanding the Development of More Durable Friction Modifiers with Sustained Friction-Reduction: Extended Tribological Studies and Oil-Aging," SAE Technical Paper 2014-01-0948, 2014, doi:10.4271/2014-01-0948.
To gain some insight into friction modifier (FM) performance retention in engine oils, we have developed a series of tribology measurements to measure and understand friction reduction performance retention by extended tribology measurements of the changes in the coefficient of friction (COF) with time. In some cases, after several days of data collection, these tests give us insight into how friction modifiers might perform in real engine operating conditions with typical long oil drain intervals. Results are presented from both a series of sequential tribology oil studies with and without FMs, as well as longer isothermal hold studies, developed using a Cameron Plint TE-77 cylinder-on-plate, and PCS-Instruments Mini-Traction-Machine ball-on-disk friction instruments. Specifically studied, were Glycerolmonooleate (GMO), Molybdenum dialkyldithiocarbamate (MoDTC), and an experimental organic friction modifier (Exp-OFM1) of a completely ashless (containing no inorganic metals) C, H, O, N surface active molecular structure. The results show the friction reduction retention can vary significantly with friction modifier type. Nitro-oxidation of the oils was also studied by tribological methods and Fourier Transform Infrared (FT-IR), to track induced changes in COF, viscosity, oxidation, and nitration, simulating oil aging.