What kind of oil does my 2000 seadoo gsx take?

the seadoo shop said to use their oil, and any other oil would result in motor failure. their oil is $50 a gallon. a buddy of mine uses oil that he gets from academy and it's only $20. i know it needs to be synthetic but seems like as long as it's synthetic then it's good!?|||just use the good brp xps or either amsoil interceptor which is 10 dollars cheeper. You need the good synthetic for the valves.