Optimizing Experimental Design to Determine Friction and Wear Characteristics of Used Oil Contaminated with E20 Fuel

The aim of this paper is to develop an experiment design to determine the wear and friction parameters of an SAE 0W20-grade reference oil and an SAE 0W20-grade used oil contaminated with E20 fuel. Wear tests in a ball–disc arrangement were conducted at temperatures and loads established using Design of Experiments. A surface analysis of the wear scars was performed using a digital microscope, while the oils were investigated using a viscometer and a Fourier-transform infrared spectrometer. Design of Experiments was further employed to develop two models using R software. For the reference oil, the developed model was only suitable for screening, while the model for the E20 fuel contaminated used oil showed a 9.8% difference between the measured and estimated coefficients of friction.