For the manual, it used a T-5. For auto, I'm not too sure. Sorry.
Mercon III
Type F Automatic Transmission Fluid.
look in the manual
Motorcraft MERCON automatic transmission fluid for your manual transmission
Motorcraft MERCON ATF ( automatic transmission fluid ) according to the owners manual
Motorcraft MERCON automatic transmission fluid in the manual transmissions on a 2004 Ford Mustang ( according to the Owner Guide )
Mercon V
There are a number of vehicles that use the T5 Transmission such as AMC Sprint, Ford Mustang, Mustang SVO, Mercury Capri, Ford Falcon, GMC Safari, TRV Tuscan and the TRC T350.
Use Motorcraft ATF
from the transmission dipstick use some adaptor so you can drop your oild inside.
The 2013 Ford Mustang runs on regular unleaded.
The 2004 Ford Mustang runs on regular unleaded.