How Much Fuel Should Be Added to a Sedan?

[LePreston]

When refueling a sedan, remember two percentages: 25% and 80%. You should refuel when the remaining fuel in the tank is at 25%, and filling it up to 80% is the most suitable. The 25% refers to the timing for refueling. When the fuel level drops to 1/4 of the tank's capacity, it's time to refuel. If you wait until the tank is nearly empty, the accumulated impurities at the bottom of the tank can be drawn into the fuel system, causing poor fuel delivery. Additionally, an almost empty tank tends to contain air, which can form condensation due to significant day-night temperature differences. This moisture can mix with the gasoline, leading to poor combustion. The 80% refers to the amount of fuel to add. For short trips in the city, there's no need to fill the tank completely, as this adds unnecessary weight to the vehicle and increases fuel consumption. Therefore, filling up to 80% is sufficient. The amount of fuel to add should also vary depending on the age of the vehicle. Newer cars generally have lower fuel consumption, so they require less fuel, which also helps in maintaining the vehicle better. As the vehicle ages, its fuel consumption will gradually increase. During this stage, the amount of fuel added should also be increased accordingly. In summary, the amount of fuel added each time is directly proportional to the age of the vehicle.

[ValerieLee]

I usually fill up the tank until the pump automatically stops. Keeping the tank around 80% full is ideal—it prevents the fuel pump from overheating due to low fuel levels while avoiding gasoline expansion overflow that could damage the charcoal canister. It's fine to fill up completely before a long trip, but for daily city commuting, filling to three-quarters on the gauge is sufficient. In fact, carrying half a tank can improve fuel efficiency. Note that the new car manual states the tank's rated capacity, but the actual fill can be about 5% more than the nominal value—no need to deliberately top it off. Gas station attendants often say filling up is bad for the car mainly to avoid customer complaints, but as long as you don’t overfill to the point of spillage, it’s not a big issue.

[VonBella]

I usually just add 200 yuan worth of gas, and this method has worked worry-free for five or six years. Keeping the fuel tank at a low level for extended periods can shorten the fuel pump's lifespan, but filling it up every time increases the car's weight and wastes more fuel. Adding a fixed amount of gas helps control the budget while avoiding running the tank empty, and you can take advantage of gas station discount days to add a bit more. When the fuel gauge shows only a quarter tank left, it's time to refuel—don't wait until the warning light comes on before looking for a gas station. Turbocharged cars require extra attention to avoid keeping the tank too empty, as insufficient fuel supply during sudden acceleration can damage the engine.

[LeSienna]

Take my advice: don't fill up the tank too much or too little. Gasoline expands when hot and contracts when cold. In summer, overfilling can cause overflow through the vent hole, damaging the carbon canister, which costs hundreds to repair. But frequently filling only half the tank is worse for your car. The fuel pump relies on gasoline for cooling, and long-term low fuel levels during highway driving may burn out the pump. It's best to refuel when two bars remain on the fuel gauge and stop at the second click of the fuel gun, leaving some space in the tank. The automatic shut-off position of gas station nozzles is very accurate, so there's no need to force a round number by topping up.

[LaPhoebe]

I've observed many car owners' refueling habits and found that the amount of fuel to add depends on the purpose. For long-distance trips, filling up until the pump stops is fine, while for urban commuting, filling two-thirds of the tank is the most economical. The gasoline in the tank is actually in a dissolved state. Consistently adding small amounts of fuel can lead to sediment clogging the filter at the bottom, but frequently filling up increases evaporation pollution. There's a recommended refueling amount on the fuel cap, and German cars requiring 95 octane or higher should be especially careful not to mix with lower-grade fuel. Remember, waiting until the tank is nearly empty to refuel is like eating only when starving—it harms the stomach and intestines.