Marvel Mystery oil is not the best, use Marvel Mystery Air Tool oil instead or any air tool oil. The purpose of the after run oil is to displace any moisture and especially nitro residue (it creates nitric acid when combined with water) and neither Marvel Mystry oil, WD40 or light machine oils do this well. Stick with an air tool oil, transmission fluid, Rislone (the one in the yellow container) or the commercial after run oils. The best buy for the buck is Rislone and it works as well as the others. do use enough each time, just a few drops wont do, especially in the 4 strokes. You must use enough to displace the moisture and nitro deposits which means enough to thouroghly coat the bearings, about a teaspoon full in the crankcase on 4 strokes. After insertion of the oil, rotate the engine as you manually rotate the prop to make sure the oil flows to all areas.