A few months ago, I took a cab from Frankfurt airport. The taxi driver had an almost empty tank and asked if it was okay to refuel before starting the trip. I agreed after he assured me it was on the way and that he wouldn't start the meter until after we got there. However, to my surprise, he only filled the tank with the minimum amount of gasoline, which likely wasn't even enough to cover our 30 km trip.
I'm still confused about this behavior. It seems especially odd since he probably had to refuel again just to make the return trip to the airport. Was this some sort of scheme to earn more money or was this just idiosyncratic behavior?