I think it just depends what is in the tank when you you pick it up. I have had test drives in Nissan, Volvo mercedes peugeot and never had to put any fuel in it. Having said that I test drove a BMW X1 from a dealership in Chester a few weeks ago only to find it was running on fumes. First stop was to a petrol station, when I told the rep on my return he just laughed and there was no offer of reimbursement. Worst experience was test driving a jaguar XF a few years ago I drove it around the corner from the dealership and it did come to a stop completely empty there was no chance of me ever getting near a petrol station. This is the one and only time I have ever run out of petrol.
The moral of the story is you shouldn’t have to pay for fuel, but check what is in the tank before you set off.