Honda SUPER CUB 125 2021 Owner's Manual page 61

Refuelling
Lower edge of
filler neck
Do not fill with fuel above the lower edge of
the filler neck.
Fuel fill cap
Arrow marks
Fuel type: Unleaded petrol only
Fuel octane number: Your vehicle is
designed to use Research Octane Number
(RON) 91 or higher.
Tank capacity: 3.7 L (0.98 US gal, 0.81 Imp gal)
#
Refuelling and Fuel Guidelines
(P15)
57