According to the 2004 Ford Mustang owners manual :
It came from the factory with a 50 / 50 mix of distilled water and
Motorcraft Premium Gold Engine Coolant ( YELLOW colored , meeting Ford
specification WSS-M97B51-A1 ) in the engine cooling system
Red, 5 year HOAT type.
The 2004 Ford Mustang has a 5-speed manual.
The 2004 Ford Mustang runs on regular unleaded.
dex-cool antifreeze is what came from the factory.
Autozone/ advanced auto usually has antifreeze that goes with either kind. I suggest that.
GreenGreen
Use antifreeze labeled as being "Dexcool approved". It'll typically be orange.
'DEX COOL' it is red in color.
For a 2004 Ford Mustang : It was the 40th anniversary of the Ford Mustang , and I believe they called the Over Head Valve , V6 engine a 3.9 liter instead of the usual 3.8 liter
Red, 5 year, HOAT type
5 year, red color.
Motorcraft Premium Gold Engine coolant (yellow colored) or similar but must be yellow