My buddy just pick up an used Buyang 300cc (actually 275 according to the manual) and I need to help him to do an oil change some routine maintenance etc.

Any suggestion on what;s the best oil to use?

Also, does these engine has an oil filter and where to pick one up?

I used to have a 110cc air-cooled but has no experience on the 300 model any tips will be very much appreciated.