What is the optimal amount to fill the fuel tank?

[MacBrandon]

The optimal amount to fill the fuel tank is up to 80% of its capacity. The impacts of overfilling are as follows: Blockage of the vent hole: Once the vent hole is blocked, negative pressure will form inside the fuel tank, leading to poor fuel supply or even a complete halt. This can result in the engine failing to start immediately after refueling. Damage to the carbon canister: The carbon canister is typically installed between the fuel tank and the engine. Since gasoline is a highly volatile liquid, the fuel tank often contains vapor at normal temperatures. The fuel evaporation emission control system is designed to direct these vapors into the combustion process and prevent them from escaping into the atmosphere. If the tank is overfilled, liquid gasoline instead of vapor may enter the carbon canister, causing potential damage.