Hi Paul and welcome to the Forum. Over here (UK) the People 50 was discontinued in 2012, but I found this on line:
“UPDATE – 2012
The WONDERFUL Kymco People 50 2-stroke scooter is no more. If you find a good previously owned one BUY IT.
If a person was to describe a perfect moped-legal scooter they would likely say it had a clean, EPA-certified 2-stroke engine for power, a CVT automatic transmission, big wheels to help combat pot holes and give a stable ride, good brakes, comfortable ergonomics, a retro-influenced design, excellent build quality and strong manufacturer/dealer support. They’d be describing the Kymco People 50 scooter.”
Suggests the 50 is a two-stroke and as such would use any good quality 2T oil. Shell? Castrol?
Found a downloadable manual at.
https://www.manuals.co.uk/kymco/people-s-50/manual?p=27