Coolant: type, capacity and separate cooling circuits
Coolant specs come in two parts: the type (which coolant to use) and the capacity (how much). Manuals describe capacity in different ways, so read the label next to the number.
Change amount or whole system?
- Change amount. Honda manuals list how much goes in at a coolant change, including what stays in the reserve tank. The 2017 Civic Sedan (2.0 L) lists 1.4 US gal, “change including the remaining 0.2 US gal (0.75 L) in the reserve tank”.
- Whole system. The 2021 Buick Envision lists 9.9 qt for the engine cooling system, with a footnote that the figure is “based on the entire cooling system and its components”. You won’t drain all of that at a normal service.
Some vehicles have two separate circuits
Hybrids can have a separate circuit for the power electronics. The 2020 Accord Hybrid lists engine coolant (1.29 US gal) and, separately, inverter coolant (0.219 US gal). Each is serviced on its own, so don’t add the two together.
Type: use what the manual names
The 2017 and 2022 Civic Sedan use Honda Long-Life Antifreeze/Coolant Type 2, mixed 50/50 with distilled water. The 2021 Envision manual says to use only DEX-COOL, mixed 50/50 with clean, drinkable water. Coolant types aren’t interchangeable just because they look alike; use the one your manual names, or an equivalent the manual allows.
Capacities are approximate. Fill to the level mark your manual describes and recheck after the engine has run and cooled.