With the axle completely buttoned up, we added two quarts of Max-Gear synthetic gear oil by Royal Purple. We picked this lubricant because it offers added protection to bearings and wear surfaces by coating them with a slippery film called Synslide. It's a term for the technology that Royal Purple developed by using a proprietary mixture of synthetic-base oil and high-tech additive compounds. We like this technology because it displaces water from metal surfaces and excels in protecting metal components in wet environments. It also fortifies the oil against the detrimental effects of heat, which causes oil to oxidize and wear out.