The problem is that the salesman who sold me the car ,said that the 2021 Civic Sport Hatchback definitely takes Regular 87 octane. The owners manual says to use Premium 91 octane, even on the gas door it say to use Premium fuel. I called the salesman after reading the owners manual and he still insisted that the car takes 87 octane. Very conflicting. I will follow the owners manual recommended fuel and use 91 octane. All salesmen are pieces of crap, even if they work for Honda .
From the owners manual. Honda Civic Hatchback Sport 2021.
Models without18 or 20 inch wheels Unleaded gasoline, pump octane number 87 Use of a lower octane gasoline can cause a persistent, heavy metallic knocking noise that can lead to engine damage. Models with 18 or 20 inch wheels Unleaded premium gasoline, pump octane number 91 or higher Use of a lower octane gasoline can cause occasional metallic knocking noise in the engine and will result in decreased engine performance.
Use of a gasoline with a pump octane less than 87 can lead to engine damage.
The use of regular unleaded gasoline can cause metallic knocking noises in the engine and will result in decreased engine performance.
Top tier detergent gasoline
Because the level of detergency and additives in gasoline vary in the market, Honda endorses the use of “TOP TIER Detergent Gasoline” where available to help maintain the performance and reliability of your vehicle. TOP TIER Detergent Gasoline meets a new gasoline standard jointly established by leading automotive manufacturers to meet the needs of today’s advanced engines.
Check out your Owner's Manual for information.