Welcome to the seadoo forum 70n70ff. Her is the spec on the recommended oil and fuel. I also believe that you should be suing the synthetic oil for you model. Is it possible to contact the old owner to see what he used? You don't want to mix types of oil, and it would be better to use what's been used in the seadoo in the past.
Use High quality low ASH API TC Injector oil.
Do Not use NMMA TC-W, TC-W2 or TC-W3 outboard motor oils or other ash less type 2 cycle oil. Avoid mixing different brands of API TC oil as resulting chemical reaction will cause severe engine damage. Never mix Mineral or synthetics oil together.
Never use fuel containing more than 10 % alcohol,( Methanol or Ethanol) as severe damage will occur. The minimum of 87 octane is recommended for most engines.
If you have any other questions give us a shout.
Karl