Your correspondent HK of Poynton reported the practice of a hire car company at Murcia airport charging for a full tank of fuel. I frequently use this airport as I have an apartment in the vicinity. I always book direct with Centauro (www.centauro.net) who allow me to return the car full of fuel. On return to the airport turn left at the last roundabout instead of going into the airport.
Continue for approx 2kms to village of San Javier and fill up at gas station at first roundabout. Centauro then credits the amount they initially charged for fuel onto your credit card. After 3 rentals you automatically get a Gold Card with benefits like free upgrades and priority queue at reception. I am approaching 80, which would normally give insurance problems with hire cars but this company has agreed that as long as you have a valid driving licence then it will accept you after 79years.