Okay! Well, no where in the manual or on the scoot does it say to use mc oil so I would have to assume any oil meeting the API recommended grade(s) would be fine.
The benefits of the 5w50 grade is its broad viscosity range, which s/b be good year-round; and possibly a longer OCI. However, since there is no oil filter just an oil screen, maybe going beyond the recommended OCI is not wise! My riding is all paved roads, mostly country roads & some highway speeds.
Which would be better, to change the oil w/conventional oil every 750-800 miles or use a good synthetic and extend the OCI to 1500-1600 miles or once a year in my case?
When you say "conventional", what do you mean?
I would not use mineral oil (there would be no harm, considering frequent interval change), but semi-synthetic or synthetic.
Personally, I use synthetic, but only because I get it at low price (around 6 US$/l).
Otherwise I used semi-synthetic, when I did not have the source where I buy the oil now.
Once again, I would like to emphasize that in the past I had a bike that did 0-100 in 3 secs and revved to 12.000 rpm, that did just fine with once per year oil changes... and semi-synthetic oil.
If it was possible, I would endorse banning all oil type and change topics on moto forums.