Polymers as lubricating oil additives can play a significant role in tribological phenomena. The main effect of the polymer addition is an increase in the lubricant viscosity and film thickness at high operating temperatures. Rheological and tribological tests were performed to determine the influence of the polymer concentration, temperature, and speed on the lubricant viscosity and elastohydrodynamic film formation capacity. A mineral oil additive with a low density polyethylene was investigated The rheological behavior of the rested lubricants was first studied for shear rates ranging from 10 to 10(3)s(-1). The low-voltage electrical resistance method was also used to estimates the lubricant film thickness formed between the rollers and the raceways in a tapered roller bearing. These experimental investigations have shown that 0.5 percent of low density polyethylene in oil is an optimal concentration which produces the highest viscosity and thickest lubricant film and hence improves the lubrication of machine elements.