Ah, I see. Thanks for the heads up, and apologies for any undue consternation! It seems it is indeed a debatable issue! There's EVEN a difference between what my owners manual days, what the Haynes manual says, and what the Triumph mechanic says! That's 3 opinions off the bat!! I can see it is a can of worms.* I think I'll chose to listen to one person....and go with it! *I am forever happy to light heartedly chew the cud with anyone or be educated, on the previso 'we are all entitled to our own opinions'....
My speed rs (2018) has Bellray 10w40 full synthetic. Only reason: that’s what my dealer uses. Not very useful maybe, but still....
I side with Dozers Dad. Any good semi synthetic oil and new filter will do fine. My personal choice is Shell semi. But it is as broad as it is long. Ride Safe Joe.