Premix?.....
If you don't know what type oil your using now, then you'll need to do a full removal and refill.
I use the Quicksilver brand of "Full Synthetic" that I get from my local Walmart. The Seadoo is suppose to use their blend of XP-S oil but I don't have a Seadoo shop close to me. The manual says if we use a different brand that it must be a non TCW-3, non NMMA, type oil. You are suppose to use synthetic in your ski.
Which ever you choose, Synthetic blend or Full synthetic, make sure you remove all the old oil before filling....:cheers: