Originally Posted by geometrician
The most important requirement in the KTM owners manual is that the oil meet "JASO T903 MA" specifications. This denotes the use in motorcycles with our engine types. See here
The viscosity of multi-weight oils is vs. actual viscosity is complex to be sure. As long as it isn't really cold (think near-Arctic conditions) or really hot (equatorial deserts) most any JASO MA oil will do.
Yeah, I wasn't sure I wanted to post anything about oil.
My point is, if you want to stick to the manufacturer's recommendation for the best performance and life of the engine, KTMs take a pretty specific and sometimes hard to find viscosity of oil. It would be nice, in a traveling bike, to have a wide range of usable oils.