I know what oil to use is an ongoing topic. Different people swear by different oils .Here is some information on
Amsoil oil for those that are not aware.

Recommended for Engines,Transmissions and primary chain case,wet clutch

Amsoil 20W-50 Advanced Synthetic Motorcycle oil

This oil meets Triumph specs also.
API SG SL/CF
JASO MA
SAE 90
API GL-1

Not recommended for shaft drive hypoid gears or where an API-GL-4 or GL-5 gear oil is required.

Additional information ,See internet, Amsoil Site

Again, there are a lot of fine motorcycle oils on the market.

Amsoil also has filters although I always use the Factory Filters. Triumph oil filters get the job done ,well made.