your bike has a separate area for oil...oil cap on right side of bike just below, and a site glass at the bottom from there...as well at the front of your bike, below the exhaust is where your oik filter goes.....and for the fule tank is just straight gasoline, i run regular gas and at times run a higher octane, I have a 1981 maxim xj 650 ...if you want pics, i might be able to help you.....plus other owners of 81 maxim xj 650....also you can go to your yamaha dealer or call them and ask for certain specs for your bike, i have where i am , and they have been helpful...as well as other owners on this site and in this discussion group....all you owners of 1981 yamaha xj650 ´s...here is my email redfordranger2000@hotmail.com ....we can exchnage pics and share info as well...this sure is a nice site...very helpful..thank you to all you owners...very helpful