20w-50 Grade men koi bi company synthetic oil nee bnaati,
agr apko yehi grade use krna hy, to mineral oil hi use krna ho ga
nd if u want to use 10w-40, then u will find semi-synthetic oils.
i m using yamaha since 1995 nd i've a conclusion that these bikes are good with mineral base oil, nd change the oil at 1000 km. Engine will never disturb u