Honda H5518H Owner's Manual page 36

Coolant
If there is no coolant in the reserve tank, check the cooling system for
leaks and repair if necessary.
m Never remove the radiator cap when the engine is hot. The
coolant is under pressure and severe scalding could result.
Add coolant to the radiator and the reserve tank, then check the coolant
level in the reserve tank after the engine reaches operating temperature.
When the engine is at operating temperature, the coolant level should be
between the MIN and MAX marks on the reserve tank. If the level is near
the MIN mark, add coolant to bring it up to the MAX mark.
Coolant Recommendation
Use high quality ethylene glycol antifreeze that is specifically formulated
for use in aluminum engines. Mix the antifreeze with low-mineral drinking
water or distilled water.
A 50/50 mixture of ethylene glycol antifreeze and water is recommended
for most temperatures and provides good corrosion protection. A higher
concentration of antifreeze decreases cooling efficiency and is recom-
mended only if additional protection against freezing is needed. A concen-
tration of less than 40% antifreeze will not provide proper corrosion
protection.
(1 Th e use of unsuitable
antifreeze, hard water, or salt water may
cause corrosion damage that will shorten the life of the engine.
CAP
COOLANT