detail it yourself and make them give you free gas tanks for your trouble or let them know you aren't happy and if not resolved you will be giving low accurate scores which hear in the states cost them money.
Or try to email/call the owner as it's sounds like the person driving as a demo should pay for any replacement parts as he didn't take car of it and should get the cheapest used car as a demo until he learns respect of others that will be buying them later.
Just remember to show the owner respect and talk comely. If not send the CEO of ford an email. The outgoing CEO took care of my 11 gt when dealer tried to void warranty, he had is office assistance take care of it and told dealer if the mustangs aren't meant to spin the tires then we should recall all of them. Only reason I still buy fords.
2014 Black 3.7 6M. 20 inch black bullets, Pypes Axle back, matte black super snake stripes, next up JLT intake.
2011 Mustang 5.0 Race Red. gone and was sick
2011 Mustang 3.7, gone sold 3 times since, that I know of.