There are several reasons why this could be possible and they are all related to the technical features of the vehicle and the laws of physics and chemistry. First things first. The specified capacity of a vehicle fuel tank does not include the capacity of the parts of the fuel supply system (the hose behind the tank cap leading to the tank), which can hold several litres of fuel, depending on the vehicle model and type.

Also, the manufacturer defines only the specified volume of the tank, which is smaller than the actual volume. Manufacturers leave additional space inside the tank for vapours and for offsetting vapour pressure. When refuelling, the tank is filled with both fuel and petroleum vapours.

In cases when the special pressure valve (the so-called breather, used to regulate tank ventilation and release emissions, button-shaped, located on the fuel filler housing) is not operational, it is possible to fill up to 10% more fuel in the tank and tank system than the capacity specified by the vehicle manufacturer. Except for malfunctioning breather, this could also be caused by either conscious or unconscious pressure applied with the fuelling nozzle to the breather on the fuel filler housing.

The volume of fuel filled is also affected by the rate of the fuel flow when refuelling. When using measuring devices and fuelling nozzles with a smaller flow rate, air is separated faster and is released through the fuel filler, leading to a delayed activation of the pressure valve and creating space for filling an additional amount of fuel into the vehicle tank.

Fuel temperature can also affect the amount of fuel that the tank can hold. As temperature rises, especially in summer, fuel density increases, so more fuel can be filled in the same tank volume. Also, during refuelling, air from the environment mixes with fuel and this can lead to foaming, especially with diesel. Under such circumstances, air stays with fuel, taking additional tank capacity, which leads to an opposite effect – the tank can hold less fuel than its specified capacity. In order to avoid such situations, INA fuels contain special additives for faster air separation and for reducing foaming.

As for LPG, here are the facts. An LPG tank features a float which activates a valve when the tank is about 80% full, preventing further filling of the tank. The float is positioned under the optimal angle and when this angle is changed, it is possible to fill the tank either less or more than the specified 80%, depending on the position of the float. Furthermore, the volume the tank can hold can be affected by difference in gas pressures between the LPG dispenser and the tank. The dispenser pump fills the tank until the pressures are equalized. During the warm summer days, when air temperature is higher and vehicles are exposed to the sun, the pressure in the vehicle tank is much higher and the tank can take less LPG than specified. Also, if the vehicle has been running for an extended period of time, at a higher ambience temperature and under heavy load, such as driving in heavy traffic, there is a possibility that refuelling LPG will not be possible at all due to the increased pressure in the vehicle tank.

For further explanations of the possibility of filling the tank above the specified capacity, please contact your authorised dealer or service representative of your vehicle manufacturer.


All measuring devices at INA retail stations have been tested and certified by a measuring authority in accordance with the applicable legislation. They are also marked with the designated labels and are installed in a way that ensures the necessary accuracy of measurements and measurement results. Measuring devices must be sealed with undamaged and designated stamps. Each measuring device must be marked with labels showing the certified period of the device – the year and month of validity of the certification.

Furthermore, all our measuring equipment for fuel dispensing is technically correct, it undergoes regular and extraordinary maintenance and meets the metrological requirements prescribed by the Ordinance on metrological requirements for flow meters for liquids other than water.

The use of the fuel dispensing measuring equipment at INA retail stations guarantees metrological accuracy even for the smallest volumes of liquid, which is displayed on the fuel dispenser as Vmin and can be 2 or 5 L.


The measuring devices are equipped with an air separator, ensuring the separation of air from fuel.

Interruptions at the fuel nozzle can be caused by a wrong position of the nozzle, as it contains a float which automatically stops dispensing fuel when the tank is full. If the fuel flow hits the tank wall directly, the return flow may stop the filling. Possible interruptions in the operation of the measuring device’s fuel nozzle do not affect the amount of fuel that is recorded on the display of the measuring device.


Any delivery of fuel to any INA retail station is accompanied by the declaration of conformity of liquid petroleum fuels. With this declaration the supplier of fuel, after conducting laboratory analysis, provides a written guarantee that the quality of the liquid petroleum fuel corresponds to the quality characteristics laid down in the Regulation on the quality of liquid petroleum fuels and the HRN EN standard.

The quality of fuel is monitored at all key stages such as procurement, production, shipment, delivery to retail stations, sales and aftermarket activities.

Quality monitoring also includes the control of certain fuel features when accepting fuel in the retail station’s storage tanks.

The fuel dispensing system is equipped with filters that prevent contamination particles from getting inside the vehicle tank.


There is no possibility of water being poured into the vehicle tank at INA retail stations. All INA retail stations are equipped with a system for monitoring the possible presence of separated water and sediment using automatic level meters. These probes continuously and accurately record the status of fuel in tanks at retail locations (displayed every minute in tenths of a millimetre).


Throughout the fuel supply chain all the way to the retail station there are checkpoints for monitoring the level of water in the tank:

  1. For each shipment of fuel, the supplier must check the shipping containers (e.g. tank trucks), which includes control of water in fuel, and then provide guarantee that the fuel is in compliance with the Regulation and the quality of liquid petroleum fuels.
  2. Each time fuel is accepted at one of INA’s retail stations, the separated water level is controlled once again before and after receipt.
  3. At the end of each business day, the results of the water control in the tank are recorded at the retail station


In addition, the system is being continuously monitored and an alert is sent when water level reaches 10 millimetres.

One should also be aware that water has a higher density than fuel, so it falls to the bottom of the tank. That is why the fuel tank suction basket is placed 20 centimetres from the bottom of the tank to further avoid the possibility of water being filled in the vehicle tank.