Andrzej

Wszystko przebiegło sprawnie i bezpiecznie. Po sprawdzeniu, zegarek oryginał.

These scammers are deliberately trying to extort extra fees or are offering cars with faulty or modified fuel meters.
I think they're either scammers or using cars with faulty or modified fuel meters.
Before returning the car to Pula airport, I filled up the tank at a station about 20 km away, until the fuel gun went out.
Unfortunately, for some unknown reason, the fuel gauge wasn't showing the maximum, and the range was still 450 km, which didn't increase after refueling. During the drive, the range gradually increased, and upon reaching the airport, it was exactly the same – 540 km – as when I picked up the car. The fuel gauge still wasn't showing the maximum, as it had been right after filling up.
The AVIA employee wanted to charge me a €45 fine. I was furious about the constant lack of a maximum fuel level indicator, but fortunately, I still had time before my flight.
I took the keys from them and drove to another station, 7 km away. I filled up with 3.6 liters of fuel, and it was pouring out of the filler neck.

When I arrived at the airport, the fuel gauge was still not at maximum, and the available range had dropped to 490 km, so I arrived at the airport anyway.

I asked how this was possible.

The explanation was unclear, and they wanted a receipt from me for filling up, about 5 euros for 3.6 liters, probably to hide evidence of tampering or the car's malfunction, so I didn't give it to them!

I emailed them asking for an explanation of how this was possible, but the reply was also off-topic, as was the current comment under my post.

Since they claim that "What matters is the gauge reading at return—nothing more.", why didn't the employee ask me again for a penalty for a low tank of fuel, since the odometer still didn't show maximum and the range had dropped by 50 km? I have photos of all the readings, and let them take me to court. I won't change my mind that they're either manipulating or offering cars with faulty odometers, as they suggest in their comment, which allows for unjustified fines to be added.

P.S.
Now I'll write, "Your accusations are false and unacceptable."
The drive to the refill station could have consumed about 1 liter of fuel because I wasn't driving calmly by then, so theoretically, there could have been about 1.6 liters less fuel at the time of returning the car than a full tank, after subtracting the fuel in the filler pipe.
But what guarantee do I have that there wasn't 2 liters less fuel in the tank when I picked up the car, since, as they themselves say, the fuel meter may be faulty. Why didn't the AVIA employee add another fine if the meter still didn't show the maximum?

They're right about one thing: "You were able to add 3.6 liters." This required numerous presses of the fuel pump, which refused to fill the filler neck all the way to the top. That would be consistent with 20 km from the first fill-up to full, and a very leisurely, legally compliant ride.

Ich habe viele Male online aus Polen gekauft.
Immer professioneller und schneller Service.
Ich bin sehr zufrieden.

Wszystko na czas i bez problemów, jestem bardzo zadowolony.

Everything on time and without problems, I am very satisfied.