Love my brand new Grand Vista 250. What's the best oil? That red stuff the racers use? What oil for Grand Vista 250?
Since it's impossible to prove that any issue later on was a result of bad quality oil,
you'll get 10 people offering 20 different oil suggestions, and all of them will say theirs
is the best, and have actually no idea why they're saying that.
Read what oil weight/viscosity ranges are recommended in your scooters manual
(we'll find one for you if you don't have it) for the operating temperatures that you
intend on riding around.
10W40 is the most likely result of that search, and ANY reputable oil brand with at least
semi-synthetic (I wouldn't be surprised if pure mineral oil worked fine too, same goes for
fully synthetic - but you'll probably be wasting your money for no good reason) blend will
do.
Think Shell, Castrol, Motul, Mobil1 and a few others.
Big price tag is a good sign too (hopefully).