a little late but I just bought a gallon of factory pre-dilute from local dealer for 14.25 out the door.

 

Check the lower radiator hoses where there are O-rings connecting the hoses to the T-joint, they leak and usually on cool down. Pressure testing on my 5.0 didn't show the leaks, I laid down under truck after it ran a while and found the leaks, helps to have a clean engine compartment to start. Also the hose from the reserve bottle is a common leak point, usually the O-ring or the clip has gone bad that holds the hose to the tank.

 

good tip jcough, no drips on floor but I'll eyeball this and keep watch on it