Why Does the Fueling Amount Exceed the Tank Capacity?

[BenjaminLynn]

Because the fuel tank capacity provided by the manufacturer refers to the safe capacity of the tank, not the maximum capacity. Here is some expanded information on the topic: Regulations: According to the 'Safety Performance Requirements and Test Methods for Automotive Fuel Tanks,' the safety performance of the fuel tank must meet the requirement that 'the rated capacity should be controlled at 95% of the maximum liquid capacity of the fuel tank.' Typically, the labeled volume is only about 80% to 85% of the maximum capacity. Fueling: Consumers can be completely assured about the quantity when refueling at China Petroleum gas stations, as the fuel dispensers are regularly subjected to mandatory inspections by local technical supervision departments, and the inspection certificates are posted in prominent positions on the fuel dispensers.

[DeElias]

Last time I refueled, I was also puzzled. The fuel tank is labeled as 60 liters, but I managed to fill it with 65 liters! Later, I asked a 4S店 technician and learned that it's normal for the actual capacity of the fuel tank to be about 10% more than the labeled amount. National standards allow for this design. This extra space is called expansion allowance, mainly to prevent gasoline from expanding and exploding due to heat, especially in summer when road temperatures can reach 50-60 degrees Celsius, causing gasoline to expand. Additionally, there's a trick with the fuel nozzle—it automatically stops when the tank is nearly full, but some people insist on continuing to press the handle, squeezing in another 3-4 liters. However, forcing the tank to be filled like this can easily damage the carbon canister, and the repair cost would far exceed the small savings on fuel. Measurement errors at gas stations are rare, but if you really suspect one, you can request them to calibrate the fuel nozzle and show you the report.

[LeJason]

I can relate to this experience. Last year during a long-distance trip, I encountered a similar situation at a service station while refueling. The fuel tank was labeled as 55 liters, but I ended up filling 59 liters. The attendant explained that it was due to the temperature of the gasoline. The underground storage tanks are cooler, around 15°C, and when the fuel enters the warmer fuel tank, it rapidly expands by about 4% in volume. They also mentioned that fuel pumps measure by volume, which is why it's common to exceed the expected amount in summer. Additionally, the fuel tank's structure is quite interesting—the fuel pump float is surrounded by anti-sloshing designs, and those curved baffles add an extra half-bottle of water's worth of space to the actual capacity. I remember one time after heavy rain, condensation formed on the tank walls, causing the gauge to show empty while allowing an excessive amount of fuel to be added.

[DelSteven]

As a veteran driver with 15 years of experience, my car has been overfilled three times. The first time I thought the gas station was cheating, but later I realized it was due to refueling a cold car. For example, when parked outside on a winter night, the fuel tank gets as cold as a refrigerator, allowing it to hold 5% more when filled with room-temperature gasoline during the day. The fuel line from the tank opening to the pump, with a capacity of about 0.8 liters, is also factored in. The key point is that the manufacturer's labeled capacity is called the safe capacity. For instance, a car labeled as 60 liters can actually hold 67 liters, with the extra space reserved for volatile gases. After changing my habit of waiting until the tank was nearly empty to refuel, overfilling has basically stopped occurring.