I have a 1996 mustang and i have a really bad problem with it. It has horrible gas mileage. I have done all the things ive been told to fix it but absolutely nothing has worked. First i did a standard oil change and that didnt help. I then changed the dirty air filter and that didnt help. I then went to my grandpa who is a mechanic and he said i needed to get a new egr valve. I was cheap so i paid to get it cleaned and that didnt work... Finally a few days ago i bought a brand new egr valve and got it installed and nothing has happened. I filled the tank up and put a bottle of RXP in and it didnt help either. I really dont know what to do to get this gas mileage fixed. Im getting around 5-6 miles to the gallon and this car is making me go broke from gas money. Any ideas on what i should do to fix it?