When choosing a cooking oil machine, you must prioritize the extraction method (cold press vs. hot press). Cold pressing preserves nutrients and flavor but has a lower yield, while hot pressing involves heating seeds to increase oil output. Additionally, evaluate the screw material, which should be made of high-strength stainless steel or Cr12 die steel to resist wear and high temperatures. Ensure the machine has an automatic temperature control system to maintain consistent oil quality and a high oil extraction rate (typically 92-98%) to maximize your return on investment.