As the final amount of petrol you will use is not known in advance and is only known after it’s been provided, the service stations need to make sure that you’re going to pay the for the entire amount. 

Therefore, as a security, they take a guarantee of between €120 and €150 on your card.

Don’t worry, the difference between the amount of the guarantee and that money will really be taken from your account will be made available on your card within 3 to 4 working days.

A little tip: try to pay at the counter if possible, to avoid these prior authorisations.