Enjay Laboratories has been conducting a continuing test program in both the laboratory and field to determine the performance of the newly introduced high quality oils. Data from this program show that these oils represent a substantial improvement over multigrade first-line lubricants available in 1961-1962. However, the new oils have been found to differ widely in performance in some cases. Further, there are reservations as to using extended oil drain intervals with even the highest quality oils. These reservations include the effects of engine aging under extended drains causing rapid sludge build-up which could lead to engine failure. In addition, the high insoluble load normally carried by these dispersant lubricants can lead to increased wear as well as the phenomenon of sludge dump-out.