We recently rented/returned a vehicle to Sixt in Dublin. Filled up the car less than 1/2 mile from location. Sixt rep inspected the car, and said everything was in order.

A week later I see an additional charge on my card for $12. Not a huge amount but I inquired and they said it was for fuel. I indicated we topped the car right before dropping off. Here is the clever response:

"With most modern vehicles it is possible to drive a vehicle more than 100km (sic) without the fuel gauge reading full.

We have also noticed that a lot of petrol stations operate high volume pumps which can cause problems when refuelling As it can cause a vehicle to stop fuelling before it is actually full due to the speed it is filled at.

Perhaps this is what happened in your case?"

I demanded that they credit the amount back, or I would dispute the charge.
No response.

I am an AVIS Chairman's Club member, and I thought I would give SIXT a try, since they were more competitive on price. Never again. Coincidentally, the NY Times just did an article on "drip pricing" by airlines, rental agencies. In this case, it was literal.