The objective of this study was to survey several types of guard bed materials for their use in hydrotreating used motor oils. The feedstock originated from numerous automobile drainings and was first reclaimed at the National Institute of Petroleum and Energy Research. The effectiveness of the four different guard bed materials was determined by studying product, guard bed and catalyst properties. The candidate guard bed materials were all tested in experiments using a commercial hydrotreating catalyst in a standard, packed bed reactor. A temperature of 325°C (617°F), a pressure of 4583 kPa (665 psi), a liquid hourly space velocity of 1 h−1, and hydrogen flow rate of 748 std. M3/m3of oil (4200 SCF/BBL) were maintained throughout each of the experimental runs. Though all of the experimental runs, except the activated clay, produced an acceptable base stock color, the greatest improvement in all properties resulted from the use of the activated carbon. The activated carbon also proved to be the most protective of the catalyst bed. The only two materials that gave undersirable results were the activated clay and the alumina spheres.