Use 10Rs Mobil oil in 100Rs fuel and 5Rs with 50Rs fuel, Thats wht i do with my Yamaha Royal, Remember running on a dry engine could prove a blundur! It can cease ur engine, Its bttr to use more mobiloil than less or no, also too much mixing wud result in white dense smoke frm the exhust pipe... so there shud a balance.
I dont recommend Rs5 fuel with 100Rs petorl as suggested by ur machenic, u shud atleast go 4 10Rs as mentioned above.