Honda CIVIC 2014 Manual page 420

Is it possible to use unleaded petrol with a Research Octane
Number (RON) of 91 or higher on this vehicle?
Your vehicle is designed to operate on premium unleaded petrol with a research
octane of 95 or higher. If this octane grade is unavailable, regular unleaded
petrol with a research octane of 91 or higher may be used temporarily.
The use of regular unleaded petrol can cause metallic knocking noises in the
engine and will result in decreased engine performance. The long-term use of
regular-grade petrol can lead to engine damage.
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