To diagnose an unknown loss of oil you need to perform a hydraulic leak down test. Your jackhead needs to be cleaned, pit can/scavenger pump needs to be empty and dry pumping unit drip pans need to be clean. Run the car up to the second floor and shut off power. Measure the oil in the tank and let the car sit for 30 minutes. If the car moves down inspect for oil on the jack head, vics, oil line, pumping unit, measure your oil in the tank. If all these check out then your oil is probably leaking in the ground either from the jack or an underground oil line.
