You could use SAE 30 non detergent oil. It should be filled to about � inch of the top, however this pump comes already fill with oil. The only time you would need to check the oil level would be if for some reason the float mechanism gets caught up and the pump runs for an extended time. It would then be good to check the oil level in the pump as well as the basin to see if some oil is present. You should expect this pump to last you a good 5-7 years or more with proper care and maintenance.