Use a standard 4 cycle MOTORCYCLE oil. I use 20-50 in mine. Whatever you do, DO NOT USE CAR ENGINE OIL. Car oils contain extra chemicals that will cause you clutch to slip. The manual specifies 3 litres for a simple change, or 3.3 litres when changing the filter as well. To check that the oil level is correct, park the bike on the CENTER STAND on level ground. I usually start my bike and let it warm up for a few minutes, and then shut it off and let it settle for a few minutes more. Unscrew and wipe the dipstick, return dipstick to hole DO NOT SCREW IT IN, remove the dipstick and ensure that the oil level is up to, but NOT ABOVE the dot. Hope that helps.