According to world statistics, up to 150,000 times a year, bad fuel is refueled in cars. This is happening every three minutes around the world and it's not just about rented vehicles. However, we said that there is a bigger chance to tank the wrong fuel if the vehicle is rented. Sometimes it may not be clear what to refuel. It is definitely not worth to improvise because the cost of repair can climb up to thousands of euros. It is unlikely that the insurance company will take care of the mistake you made. It is really not worth taking the risk in this case and it doesn't matter if the car is your own or rented.
Most of the faults occur when gasoline is refueled into diesel fuel tanks. The narrow gasoline hosepipe can easily fit into the wider diesel car tank. So if you refuel gasoline into the diesel fuel system. Diesel acts as a lubricant for the engine, but gasoline behaves more like a solvent that increases friction. This can damage everything in the system, from the fuel pump to the filters and fuel injectors. Of you find that the fuel has been refueled into a diesel car, do not start the car. Do not even switch the ignition because that may cause that the fuel will be pumped into the fuel pump. If it is possible to move the car without starting, move the car away from the gas station. You can ask a gas station employee for help. Then you need to call a car rental when you have a rented car.
So we already know that refueling bad fuel into a rented car can cause very many problems. It is important to make sure that you know what to refuel in the car. If you have forgotten this information, the easiest way to find out is to call the car rental company and verify what to refuel. The important thing is that if you are not possible to reach car rental for any reason, you have a few different alternatives to protect you before refueling the car with the wrong fuel:
Label information - manufacturers usually provide information about the fuel type with a sticker on the fuel tank, on the car keys or on a dashboard;
Information directly on a fuel tank - When the sticker is missing, it should also be written on a fuel tank;
Shortcuts - Cars with a diesel engine are usually labeled with a D (for example TDI, HDi)
It is definitely worthwhile to measure twice and cut once in this case.