When procuring a used oil refining machine (waste oil distillation plant), you must prioritize processing capacity (TDP), typically ranging from 1 to 50 tons per day. Ensure the machine utilizes high-vacuum distillation technology to lower boiling points and prevent oil cracking. The heating system should be versatile, supporting diesel, natural gas, or electricity. Crucially, verify the yield rate, which should ideally be between 80% to 90% for high-quality base oil or diesel, and check for stainless steel 304/316 construction in condensers to prevent corrosion from acidic waste.