I was over on the Bonneville forum the other night (remember I do have a Bonneville too) and....
CC Rider, the moderator on the forum admitted that he didn't use Mobil 1 XT4 or whatever the oil is that is only sold at the dealer and costs more than Amsoil, but Triumph stated after exhaustive tests, the Mobil was the best for the bike (wonder if Bloor has stock in Exxon-Mobil?)
Mr. CC uses.....ready for this...Shell Rotella T 15-40 and has for over 70 thousand miles in his T100 and his Thruxton. Seems a couple of other posters over there also use that and Shell Synthetic Rotella 5-40.
There was great discussion about the Rotella's and I'm no chemist but I do know that automotive lubricants made today don't have the phosphorous and zinc additives in them because of Gummit emission standards whereas the H.D. Diesel oils do.
CC went on to say that he changes his oil every 3 thousand miles and every time he pulls the valve cover, the overhead is clean and shows no blow by or varnish. The T100 is air/oil cooled, not water, so there would be more variation in temperature extremes than with the R3 and it's water jacket.
So, in summary, why not use Shell Rotella 15-40 at less than 10 bucks a gallon or Triumph recommended Mobil at 40 bucks plus. Even with 3K oil changes, you'd be 10 bucks ahead with Rotella and flushing the contaminants out every 3K instead of every 10K. 3K sounds better to me. Besides, Rotella is available everywhere and the Mobil is hard to get (only at dealers). For sure, I'm going to switch my T100 from Amsoil to Rotella. I ride it less than 3K per year anyway.
This ought to be a good one for discussion as opinions about oil are like butt holes, that is, everyone has one.