Honda FourTrax Rubicon TRX520FA5 2020 Owner's Manual page 154

Engine Oil & Filter
7. If the oil level is near or below the lower level mark, remove the
seat (page 132) and the tank cover assembly (page 134). Remove
the engine oil fill cap (8) from the front right crankcase cover and
add the specified oil into the fill cap hole, up to the upper level
mark on the dipstick.
Do not over fill.
8. Reinstall the engine oil fill cap and dipstick.
9. Install the tank cover assembly.
10. Install the seat.
11. Install the oil check lid.
NOTICE
Running the engine with an improper oil level can cause serious
engine damage.
RIGHT SIDE
144
Servicing Your Honda
(8) engine oil fill cap
(8)