Arrived at location on 7/21/22 - Checked over unit, pilot is lit, turned thermostat to 300F and let heat, when thermostat cycled off the oil temp was 22F over thermostat setting. Turned thermostat to highest setting of 375F and let heat again. When thermostat cycled off oil temp was 19F over. Let thermostat cycle a few times. Oil temperature remained between 15-19F over, thermostat will need to be replaced. Hi limit should also be replaced as it appears to be the original which could be contributing to their intermittent issue. Returned to location on 8/5/22 - Removed failed hi limit and thermostat, installed new hi limit and thermostat, lit pilot, turned on thermostat. Let heat, unit heated up and thermostat is cycling, confirmed unit working correctly at this time.