I just picked up some oil from my Triumph dealer. I found out that Triumph has changed their recommended oil. They are now recommending Castrol RS 4T 10W-50 instead of the Mobil 1 4T 15W-50. I didn't pay attention to the viscosity change only the brand. I bought 3 quarts as I had one of the Mobil left from my last change. I assume there is no problem mixing 3 of the new with 1 of the other. They are both fully synthetic 4T. The new Castrol oil is supposed to be a better wet clutch oil (RS - reduced slippage) proposed to get more power out of the bike.
Anyway, I guess I'm going with Triumph's change. The cost was about $11. a quart.
