My thoughts on this....
I'm married to an engineer who works in the oil industry so I get to mix with people in the industry. I spoke to an oil specific chemist at a work function...he had a PhD in his field so he really knew his stuff.
The big deal he pointed me toward was just to change the oil more frequently than is specified. Don't get a crap $10 for 40 litres of something that had previously been used to cook up French fries, but the specified brand in the manual is there because that company paid to have its brand included as the factory recommendation.
He mentioned Shell oil was once the whizz bang go to spec stuff for ktm...and then 1 year another brand got the rec, even tho the motor hadn't changed, nor had the oil formula. Why? $$$$ that's why. Shell had apparently told them that the product could stand on its own reputation.
I went with a good quality ester oil. Many $$ cheaper, and it's a 15/50 synthetic. It's a pretty warm climate here so I don't need anything on the lower scale.
I should say I have had numerous Ktms, both 2 and 4 stroke. I've never used the oil ktm recommended, just a good quality, but much cheaper brand.
I ride my bikes hard in tough desert condition in temps well in excess of 100 degrees for much of the time.
I have never blown a motor...although I frequently boiled them.
I ran the exc's well over 30 000 kilometres before rebuilds.
Just my philosophy....I always say, " I buy my bikes to ride, not to pose on". So they don't get much love I'm afraid!