Here is the link to the service manual for your scooter.
The Fa50 has a two stroke motor, which means that the oil is mixed with the fuel to lubricate the engine parts and also in this case the bearings except instead of mixing the oil and fuel before you fill the fuel tank, the Fa50 uses Suzuki's CCI system where the oil is pumped in for lubrication. The oil level will need to be checked every time that you put fuel in, more often if you seem to be blowing a lot of smoke or however often once you have worked out your oil consumption rate .
Here is a description of how CCI works.
Hopefully this is of some help.