The full cooling system of a 2018 Honda Civic typically holds about 6.5 to 7.0 quarts (roughly 6.2 to 6.6 liters) of coolant. The exact amount can vary slightly by engine variant and market, but that range covers most 1.5-liter turbo Civic models from that year.
When planning a coolant change or a routine top-off, it helps to know the total capacity, the correct coolant type, and the proper refill procedure. Below is a detailed guide to capacity, product choice, and how to refill and bleed the system to maintain cooling performance.
Estimated cooling-system capacity for the 2018 Civic
Key figures to know when planning a coolant change:
- Total cooling-system capacity: about 6.5 to 7.0 quarts (6.2 to 6.6 liters).
- Coolant type: Honda Genuine Long Life Coolant Type 2, mixed 50/50 with distilled water, or an equivalent that meets Honda’s specification.
- Mixing rule: Do not mix incompatible coolants; use the recommended ethylene glycol-based coolant in the specified ratio.
- Bleeding the system: After refilling, bleed air from the system to prevent hot spots; operate the heater and monitor for smooth temperature cycling.
Note: Engine variant and regional specifications can cause small differences. Always consult the owner’s manual or service manual for the exact capacity for your trim and engine code.
How to perform a coolant drain and fill (step-by-step)
Below is a standard approach used by many technicians. If you are unsure, consult the service manual or have a professional service shop perform the change.
- Ensure the engine is cool; park on a level surface and place a drain pan underneath the radiator.
- Open the radiator drain valve or disconnect the lower radiator hose to drain the old coolant completely; collect it for proper disposal.
- Close the drain valve or reattach the hose once the system is empty.
- Pour in pre-mixed 50/50 coolant until the coolant reaches the proper level on the expansion reservoir.
- Start the engine with the heater on high; remove the radiator cap (if accessible) to vent air, and allow the thermostat to open; watch for air bubbles and continue adding coolant to maintain level.
- Shut off the engine after the thermostat cycles and the coolant level stabilizes; allow to cool and recheck the level; top off if necessary.
- Dispose of old coolant according to local environmental regulations.
Conclusion: A full drain-and-fill on a 2018 Civic generally requires about 6.5-7.0 quarts of coolant, and the system should be refilled with a 50/50 premixed mix. Bleeding and checking for leaks are essential parts of the process.
What coolant should you use?
Always use the coolant specified by Honda to ensure proper corrosion protection and compatibility with the cooling system materials. For most 2018 Civic models, that means Honda Genuine Long Life Coolant Type 2 (50/50 premixed) or an equivalent meeting Honda’s specification. Do not mix different coolant types, and never use water alone as a long-term substitute.
Summary
For a 2018 Honda Civic, plan for roughly 6.5-7.0 quarts (6.2-6.6 liters) of coolant for a full cooling-system refill. Use a 50/50 premixed coolant as recommended, bleed the system to remove air, and verify the level after the engine has cooled. If you are only topping up, you may need a smaller amount to bring the level back to the full mark.