ABSTRACT
Nowadays, there is an increasing trend to use synthetic oils to lubricate automotive engines working under severe conditions. To overcome the fact that synthetic oil is more expensive than mineral oil it is proposed to use blends of the two oils. 
 
The present work aims to investigate the antiwear properties of mineral and synthetic oil blends. The tested oil blends with different concentrations were preheated to 100 ^◦C for 50, 100 and 150 hours. Testes were carried out to investigate the effect of preheating on the antiwear properties of steel lubricated by the blends. Cross pin wear tester was used in the experiments.
 
Based on the experiments, blending mineral oil by synthetic oil should be followed by a preheating process. The best wear resistance can be obtained by preheating the blends mineral and synthetic oil for 50 hour at 100 ^◦C. Addition of synthetic oil to mineral oil up to 70 % can significantly reduce wear. Abrasive wear was reduced through increasing the preheating time up to 50 hours. As the grit size increased wear increased. This behaviour was attributed to the increasing embedment of sand particles in the steel counterface.