I was actually searching on EOS for the same answer when I found your question. A lot of the posts I found were a few years old and the companies recommended have now joined the bandwaggon.
I've just returned from spain and got ripped off from Gold Car and have vowed never again. We drove from Marbella to Sierra Nevada near Granada return and only used 3/4 tank as it was diesel. My findings before finding this post were -
marbesol full/empty unless you go for unlimited option but this costs substantially more.
malagacarhire full/full However in insurance section it mentions Niza Cars will take 300 Euro deposit on insurance. I wonder if fuel policy is also different and you won't find out until you arrive.
autosflores return with same fuel, however this is a small company.
It's a shame the comparison sites dont allow you to exclude full/empty companies. It encourages people to drive for the sake of it, to get there moneys worth - hardly environmentally friendly !
Will watch this post with interest! Regards, Simon