I have a 2004 6.0. It has been between -10 and 20 degrees where I am and my truck has been starting and running fine until today. I started it up and it ran for a few minutes then died. I started again and ran and quit while I was driving. I got it parked, ran to the auto parts store and bought some 911 fuel additive and some anti gel. Followed instructions on the bottles. Fired right up, got warm so I shut it off. Came back about an hour later and it wont start at all. It tries but it will not fire up. Any thoughts?