Honda Civic Owner's Manual page 302

Engine Coolant
RADIATOR CAP
Si
3. Remove the radiator cap by
pushing down and turning
counterclockwise.
296
RESERVE TANK
Except Si
The coolant level should be up to
4.
the base of the filler neck. Add
coolant if it is low.
Pour the coolant slowly and
carefully so you do not spill any.
Clean up any spill immediately; it
could damage components in the
engine compartment.
5. Put the radiator cap back on, and
tighten it fully.
RESERVE TANK
Si
Pour coolant into the reserve tank.
6.
Fill it to halfway between the MAX
and MIN marks. Put the cap back
on the reserve tank.
Do not add any rust inhibitors or
other additives to your vehicle's
cooling system. They may not be
compatible with the coolant or
engine components.