We use synthetic Shell Rotella T6 15w-40 in the Summer and synthetic Valvoline Ultra Powersport 4-stroke 10w-40 in the Winter here in West Michigan. Both are JASO MA/MA2 certified and have high levels of zinc that supports wet clutch designs. We've NEVER had any engine problems related to using this oil and it's our go-to when servicing customers' machines. Hope that helps... 😉