For my part, I don't think Goldcar are any worse (or better) than many of their competitiors. It's just difficult to find ONE Company that is reliable and treats you as a sensible person.
I booked over the internet and found Goldcar to be one of the cheapest, 47 euros for 9 day hire, nil excess etc from Almeria airport.
However, when collecting I was charged 81 euros for a full tank of diesel, in a Fiesta...
So, I did a lot of driving, trip to Murcia IKEA from Mojacar etc. On the way back, the full low light came on about 30km from Mojacar so I put 10 euros in only to see the fuel gauge register as one third full!!! So, at best a full tank would be less than 40 euros, so how on earth do they get away with charging double the cost at a petrol station (and no doubt they arrange a discount rate for their fuel!
I'd like to see a website where not only the basic rental price is shown, but the cost of fuel and "extras" such as additional drivers, child seats etc.
If you booked a Ryanair flight for pennies and then found you had to pay again on boarding for a seat, there would be an outcry, yet rip off fuel prices are just as outrageous.