I plan on getting a WaveRunner for this summer. I will probably be buying a used one rather than trying to get my hands on one that is brand new, since that is somewhat expensive. My only concern with having a used one is that the maintenance on it may not have been done properly in the past. I will want to drain all of the gas and oil to start at least somewhat fresh.
I know that you can technically use any one of many different oils in a WaveRunner, but I would rather use Yamaha oil that is specifically engineered for use in WaveRunners. I just think that having oil that is actually made for the item that you are using is always better than choosing oil that will work, but isn’t designed to be used specifically with the engine.