Honda Civic Service Manual: Engine Cooling

Engine

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Coolant Replacement (R18A9)

1. Radiator Cap 1. Wait until the engine is cool, then carefully remove the radiator cap. ...

See also:

Honda Civic Owners Manual. Recommended Engine Oil
Genuine Honda Motor Oil  Premium-grade 0W-20 detergent oil with an API Certification Seal on the container. Oil is a major contributor to your engine's performance and longevity. If you drive the vehicle with insufficient or deteriorated oil, the engine may fail or be damage ...