It's been a very long time ago, but I used to rent a Commander 114 out of Addison with some club, don't even recall the name now.
What I do remember is that you rented the aicraft "dry". The procedure was to call a particular FBO (not Million Air), designated by the aircraft rental company and top off the aircraft (to the tabs). You then paid for your fuel with the rental company, who in turn paid the FBO. This procedure made me a little suspicious so I called the FBO on my own and ask what my 100LL fuel price would be if I was not a transient customer but Addison based. I was NOT suprised to find that the fuel price they quoted me was SIGNIFICANTLY less than what the rental company charged me. Needless to say, it was the last time I ever rented there again (or used that FBO for that matter).
Word to the wise y'all.