I have been hiring cars several times a year in spain for a number of years now and have noticed that it is nigh on impossible to locate a renter who offers a 'full full fuel policy' i.e. a full tank of petrol is charged to credit card but reimbursed when car is returned with full tank of fuel. Car hire companies charge an expensive rate for fuel and make further profit when the car is returned with petrol. I have been in the position several times whereby I have only used a half tank of petrol but paid for an expensive full one. However, I think you may have the advantage as you are renting 3 vehicles and there may possibly be room for negotiation. On one rental for 3 days I contacted a few agents via mail to request a full full fuel policy and found Carjet very helpful. Hope this helps.