Changes of engine oil flow properties during its life cycle

Abstract

The work is focused on quantification of influence of operation on flow properties of motorcycle engine oil. Three different kinds of synthetic engine oil (MOTUL) were tested, namely unused oil, run-in oil (650 km after engine reboring) and regular engine oil (6200 km of motorcycle operation). The samples were frozen to below zero temperatures and kinematic viscosity was continuously monitored in the range of -5 °C and +115 °C Consequently, the kinematic viscosity at reference temperatures of 0, 40 and 100 °C was compared. Viscosity was measured by digital viscometer with concentric cylinders measuring geometry. The biggest difference occurred in case of lower temperatures where e.g. at 0 °C decrease to 29% and 43% of its original value was detected for used oil and run-in oil respectively. Flow behavior was modeled using several mathematical models -Arrhenius equation, exponential, and Gaussian equation. The best match between experimental and computed data was received in case of Gaussian fit with R2= 0.997 and 0.992 for run-in and used oil, respectively. The models are generally usable for description of rheological behavior of given engine oil.