Just bought my first super duty, 2011 f350 6.2 with 141000 miles. The previous owner had either used green or a universal coolant. So one of the first things I did was flush the system and refilled with ford orange. I only opened the drain valve on the radiator system since the plug on the block was very rusty and I wasn’t about to try to get that out. I drained, filled with distilled water, ran the truck with heat on, then drained again. I repeated this until all water coming out was clear and a few times after that.

There wasn’t a coolant capacity stated in the owners manual and even the ford dealership couldn’t find it in there computer system. I found a few “specs” online stating the system took somewhere between 5-6 gallons. I know that a decent amount of water stays in the block and heater since I didn’t pull the engine plug. After the final drain, I was able to put 3 gallons of concentrate into the system until it met the full line. So if the system takes about 6 gallons then I should be okay as far as having a 50/50 mixture? I bought one of those cheapy floating ball testers and 4 out of 5 floated which according to the scale meant I am good up to -25 degrees Fahrenheit