Why does the Civic's 47-liter tank only require 37 liters to fill up?
4 Answers
The reason why the Civic's 47-liter tank only requires 37 liters to fill up is that there is typically about 10 liters of engine oil remaining in the car when the system prompts for refueling. Therefore, only 37 liters need to be added to reach full capacity. Below is detailed information about automotive engine oil: Overview: Engine oil, also known as engine lubricant (English name: Engine-oil), has a density of approximately 0.91×10³ (kg/m³). It serves multiple functions including lubrication and wear reduction, auxiliary cooling, sealing and leakage prevention, rust and corrosion protection, as well as shock absorption. Composition: Engine oil consists of two main components - base oil and additives. Base oil forms the primary constituent of lubricants, determining their fundamental properties. Additives are used to compensate for and improve any deficiencies in the base oil's performance while imparting new characteristics, making them an essential component of lubricants.
I totally relate to this issue. Last time when I refueled my friend's Civic, I noticed the same situation. The manufacturer's claimed 47-liter fuel tank actually refers to the safe capacity, meaning that's the real amount of gasoline it can hold. About 10% of space at the top of the tank is reserved for gasoline vapors to prevent expansion due to high temperatures and avoid tank rupture. The fuel nozzle automatically shuts off when it senses the fuel level approaching the filler neck, at which point the tank isn't actually 100% full. Additionally, the fuel pump is cooled by being submerged in gasoline, and overfilling might damage it. From my several actual tests, refueling when the low fuel light is on usually takes about 35-38 liters, which is completely normal. It's safest to stop refueling when the nozzle automatically shuts off and not try to force more fuel in.
As a car enthusiast, I've studied the Civic's fuel tank design. The 47-liter capacity is a theoretical value. During actual refueling, the sensor at the front of the fuel nozzle stops when it detects fuel vapor to prevent overfilling. The internal structure of the fuel tank is complex, especially the curved pipe from the filler neck to the tank, which can hold a significant amount of fuel. When the fuel gauge shows the yellow warning light, there's actually about 10 liters of reserve fuel left. Temperature also plays a role; in cold weather, gasoline has a higher density, allowing slightly more fuel to be added. Based on my tests, the first refuel of a new car can reach nearly 42 liters, but subsequent refuels usually fluctuate around 38 liters. There's no need to worry about gas stations shortchanging you.
Many car owners are puzzled by this during repairs. The nominal fuel tank capacity includes a safety margin, similar to how mobile phone batteries are labeled. An empty Civic can indeed hold nearly 53 liters, but the manufacturer recommends a maximum fill of 47 liters. If it only takes 37 liters to fill up, this indicates calculation errors in remaining fuel: either the fuel float is stuck in a higher position or sediment at the tank bottom is occupying space. I once helped a customer fix a case where the fuel gauge sensor malfunction caused display deviations. Regular use of fuel system cleaners is recommended to reduce sediment buildup.
