A diesel lube tech is an automotive specialist who deals with making sure that diesel engines remain oiled so that they can stay in top shape. Your duties and responsibilities include inspecting vehicles with diesel engines, such as heavy-duty construction equipment, forklifts, farm tractors, tractor trailers, or diesel engine trucks, and making sure that all of the moving engine parts, as well as any other moving parts in the vehicle, are lubricated with grease or other recommended lubricant. You also check vehicle fluid levels, change oil, and replace oil and air filters.