Any oil that meets Triumph Specification should work fine. The Bobber Black manual states: Fill the engine with a 10W/40 or 10W/50 semi or fully synthetic motorcycle engine oil that meets specification API SH (or higher) and JASO MA, such as Castrol Power 1 Racing 4T 10W-40 (fully synthetic) engine oil, sold as Castrol Power RS Racing 4T 10W-40 (fully synthetic) in some countries.

The API SL listed on the bottle is higher than API SH and the JASO MA rating meets requirements. It appears this oil would be fine in your motor/transmission.

 

One other note, those ratings on the oil are not some arcane lingo. API is American Petroleum Institute and JASO is Japanese Automotive Standards Organization. When API is specified it is ALWAYS a letter designation that is backward compatible. So if the oil must meet SH standards, any oil with a higher letter designation is a newer oil that meets the older standard, therefore any newer oil is backward compatible to the older oil when the engine/transmission was developed. The JASO rating is primarily for the clutch friction qualities required for wet clutch performance. So for best clutch performance JASO MA2.

 

They have been making bikes in Japan for a long time, I don't think they would skimp on quality. I mean there are thousands and thousands for their commuting needs

 

They can claim its full synthetic but it should always say quadruple ester.. I use mostly that but add a 1/2- 1court of royal purple oil as it's compatible and has a ton of oil based detergent
Chevrone gas is good answer but only in the throttle , tank, and cumbustion chamber.
Royal purple helps with cleaning out the other areas of the engine.

 

They can claim its full synthetic but it should always say quadruple ester.. I use mostly that but add a 1/2- 1court of royal purple oil as it's compatible and has a ton of oil based detergent
Chevrone gas is good answer but only in the throttle , tank, and cumbustion chamber.
Royal purple helps with cleaning out the other areas of the engine.

Royal Purple also has a heavy dose of friction modifiers that may affect clutch performance so be judicious, otherwise great lube (has best pressure performance of any oil).