Like the thread title says.. I have a KTM 990 SM-T and recommended oil (above 32F) is 10w-50 Motorex or 5w-40 Motorex at lower temps. The KTM dealer doesn't even stock the 10w-50, instead recommending 10w-40 or 15w-50. Brand isn't my issue at all, but the grade is. At $16/liter, the Motorex is simply cost prohibitive. The problem is that every other 10w-50 is very near that price and all are tough to source easily. (The dealer is 70 miles away) At the moment, it has 15w-50 in it, but I'd like to find a cheaper and quality alternative. I've read the articles on the site until my eyes have bled...so I'm looking for experienced opinions. Will 10w-40 give me problems if I'm riding on the street and highways at a sane pace? (Engine speeds around 5-6K RPM for extended periods, with accel rpm up to 9K) I can get 10w-40 4T Mobile 1 locally and at a reasonable price. I can get 15w-50 Mobile 1 (auto) for a few bucks less and I run it in my Triumph already, which is correct grade for it. It seems to me that the 15w-50 would be wear things more on start, but the 10w-40 may require more frequent changes. Maybe I should just try the 10w-40 and get it analyzed. And yeah...I've tinkered with the 5w-40 Rotella idea too....it never ends. PS, please be gentle, I'm new here.