Many of us use a green coolant. It's easy to find and likely nothing else is less expensive. I happen to use good ol' Prestone. I buy it at Walmart. If I'm out of town I know I can find good ol' Prestone almost anywhere coolant is sold. Prestone has now re-branded it, and it's now marketed as Prestone All Vehicles Antifreeze.

Prestone | Products

As for your reference to 50/50, the target ratio for antifreeze to water is 50/50. Some companies, Prestone included, now sell their products pre-blended. That's not what I use; I buy Prestone All Vehicles Concentrate.

Here's the procedure I follow.

• Pull the lower hose from the radiator and let it drain. It'll be messy; be sure to use a BIG catch pan. This will remove roughly 50% of the coolant that's in the system. The remainder will still be in the block, etc.
• Reattach the hose and fill the system with with water only. Some people say to use distilled water. Distilled water is very inexpensive so use it if you like.
• Follow the Refill procedure described in the RAVE, meaning release the coolant reservoir from its mount and raise it so its lowest point is above the tee fitting with the bleed screw. Open the bleed screw and fill the system from the reservoir until water begins to flow from the bleed screw hole. Replace the bleed screw, then replace the reservoir in its mount.
• Drive the truck a few miles to ensure the water you used to refill the system gets thoroughly mixed with the old coolant that was left in the system.
• Repeat the process as many times you need to until there's no visible color left in the coolant/water you drain. For my truck that usually takes 2-3 cycles. At that point the system will be very, very close to having only water in it.
• At that point, drain it again as completely as you can and refill with two gallons of Prestone Concentrate, not the 50-50 mix. That will give you, with the water that's left in the system, very close to the 50-50 mix that is your target.

 

Just make sure to get ALL of the DexCool out of the cooling system. It doesn't mix well with glycol type liquid coolant. The Brits over here love DexCool but in my past military career we had too many clogged coolant systems in our aircraft generators, light carts and air compressors due to DexCool coolant.
For the record, I prefer Valvoline's Zerex G05 in my V8.