Engine Coolant (for gasoline engine versions)
Adding Engine Coolant

If the coolant level has dropped to the MIN mark or below, add coolant and bring the level up to the MAX mark. Check the cooling system for signs of coolant leakage.
Use only Honda All Season Antifreeze/Coolant Type 2. This coolant is a 50/50 mixture of antifreeze and water. Do not add undiluted antifreeze or plain water to the cooling system.
Unsuitable antifreeze may cause corrosion damage to many cooling system components made of aluminum alloy.
Some antifreeze brands available on the market, despite manufacturers' claims that these products are neutral to aluminum, do not provide adequate corrosion protection for aluminum components.
If there is no coolant at all in the reserve tank, check the coolant level in the radiator.

WARNING
Do not remove the radiator cap while the engine is still hot. Doing so may cause severe burns from hot coolant spray or steam.
Do not remove the radiator cap until the engine and radiator have cooled.

1. Make sure the engine and radiator have cooled down.
2. Without pressing down on the radiator cap, turn it counterclockwise to the stop so that the pressure in the cooling system drops to atmospheric pressure.
3. Press down on the cap, turn it further counterclockwise, and remove the cap from the filler neck.
4. The coolant level in the radiator should be flush with the base of the filler neck. If necessary, add coolant to the radiator.
Add coolant slowly and carefully to avoid spilling.
Wipe up any spilled fluid immediately, as it may damage components located in the engine compartment.
5. Install the radiator cap in place and tighten it securely.

6. Add coolant to the reserve tank. The coolant level should be midway between the MIN and MAX marks.
Install the reserve tank cap in place.
Do not add any supplemental corrosion inhibitors or other additives to the coolant. These products may react with the coolant or be aggressive toward the materials of the engine or radiator components.
Test yourself
A quick Honda Civic quiz: every answer comes with an explanation and a link to the manual page.