How much radiator fluid do I need to put in a 95 3.8 v6 mustang upon changing it?

I put 2 gallons, the guy at advanced said 3, but two seemed like plenty. What happens when u put to much?How much radiator fluid do I need to put in a 95 3.8 v6 mustang upon changing it?fill it till its full then run it with the cap off till it burps then top it off, it takes what it takesHow much radiator fluid do I need to put in a 95 3.8 v6 mustang upon changing it?fill it until its full, run it while engine is cold with the radiator cap off, it draws it into the engine, leaving you the room to fill it all the way again.... you wont put too much