The elimination of lead from used motor oils is performed by ultrasonic lixiviation using nitric acid, the lead being recuperated as lead sulfate during the acid regeneration. Beside the treatment of waste oils by the traditional methods, this new processing way gives alternative routes, not used usually for waste oils, such as introduction through the blowpipes of a blast furnace, addition to the coal in coke oven plants, coprocessing with coal in liquefaction or gasification plants, or even in copyrolysis with coal.