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.