Honda Pioneer SXS500M 2018 Owner's Manual page 128

Engine Oil & Filter
6. If required, add the specified oil into the fill cap hole, up to the
upper level mark on the dipstick. Do not overfill.
7. Reinstall the oil filler cap/dipstick, rubber dust cover and seat
bottom.
NOTICE
Running the engine with an improper oil level can cause serious
engine damage.
118 Servicing Your Honda