TR6, doesn't look like anyone answered your question. There is NO 15W50 Motorcycle oil yet that I've found in the US market besides the MX4T through the dealer. The only other MX4T so far seems to be either 10W40 or 20W50, both the wrong viscosity (per the manual). The 15W50 seems to be a European-market specific oil (funny, you can buy 15W50 Mobil 1 for our cars over here, too bad they can't do the same oil with a the correct motorcycle additives package, but Triumph probably has an exclusivity contract with Mobil 1!)
