Diesel truck oil in a motorcycle?

I bought a KTM 520MXC last weekend. The guy I bought it from is a KTM fanatic and he runs Rotella T 15W40 diesel truck oil in his four stroke bike. He has a 2003 KTM 525 with well over 1000 hours on it, and he uses the Rotella T in that as well. Is this something that a lot of people do? Does anybody have an... show more I bought a KTM 520MXC last weekend. The guy I bought it from is a KTM fanatic and he runs Rotella T 15W40 diesel truck oil in his four stroke bike. He has a 2003 KTM 525 with well over 1000 hours on it, and he uses the Rotella T in that as well. Is this something that a lot of people do? Does anybody have an opinion on this? I have always ran Spectro 10W40 in my four strokes.
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