Last month I drafted a Thread entitled "Rotax Engine Oil" which set forth many manufacturers of oil that make a Low Ash API TC rated oil, they type that is recommended in your SD Operators Guide.
Depending on the part of the country you live will dictate which brand is available.
I have the same engine as you, bought new. In 2005 I started using Valvoline TCW3 oil in one of my GTX's and last month when I had to pull the engine to replace a defective crankshaft I was told by the shop that sold me the CS that my bearings had signs of overheating.
Albeit it was the mechanics opinion that the overheating was caused by the oil I use, I didn't agree.
That said, my other Doo has never had a problem, so, to be on the safe side, I'm going back to spending the additional $16 a gallon and hopefully, I won't be replacing another crankshaft.
Albeit I learned a lot doing it, my wife got tired of hearing me swearing under the shade tree when I couldn't find a screw or part.