When sourcing a mustard oil expeller, you must prioritize the oil residual rate in cake, which should ideally be below 6-7% for maximum efficiency. Look for machines equipped with high-carbon steel screws and squeeze bars that have undergone vacuum heat treatment to ensure wear resistance and a service life of at least 5,000-8,000 hours. Additionally, verify the processing capacity (kg/h) matches your production scale and ensure the motor is 100% pure copper wire to prevent burnout during continuous high-load operation.