The Effect of Fuel Contamination on the Wear Characteristics of Used Motor Oils

Abstract

There are many contaminants that could lead to the alteration of oil viscosity. Diesel fuel is one of the deteriorating contaminants for diesel engine oils. It is among the main factors that give high impact towards the deterioration of engine oils as one study has found that, in average, 0.36% of total fuel consumption ends up in the crankcase. Many studies have demonstrated the effect of fuel dilution on the wear characteristic. However, there are limited studies that focused on the percentage amount affecting the wear characteristics together with other influencing factors such as load, speed and temperature. In this research, used motor oil - Gibson 20W50 had been mixed well with fuel percentages of 0, 1, 3, 5 and 7, hence creating 5 samples that were run under different speeds. The experiment is conducted by following the ASTM 4172 standard. Based on the results, the fuel contamination in used motor oil was considered limiting at 5% contamination and became totally deteriorated at 7%. Through a Stribeck Curve, it could be understood that wear is inversely
proportional to sliding velocity, where it is one of the lubrication parameters together with speed and load. Rough surface on the balls indicated that abrasive wear has occurred due to the use of used motor oil.