New Pro Honda HP4S is Honda's first fully synthetic four-stroke motorcycle oil and was quite literally years in the making. HP4S offers lower friction than conventional oils, better oxidation resistance for better high-performance, higher film strength and quicker flow to vital engine parts at low temperatures, especially during startup. And best of all, HP4S provides maximum power due to less frictional drag. HP4S is approved for use in all 2006 or newer motorcycles, ATVs, Scooters and PWC. It is, quite simply, our very finest four-stroke oil. HP4S is compatible with synthetic blends such as HP4, as well as regular petroleum oils like GN4. There is no need to flush the crankcases before switching to HP4S.