Originally Posted by jeepjones
To make it real easy, just buy the premixed 50/50 coolant. That way you don't have to go through the "mess & guess" BS when mixing it.
Using the pre mixed will throw off the water/antifreeze ratio as there is going to be water leftover in the block. Unless you pull the block drain plugs you will have to quite a bit more water. Pulling the drain plugs is an even bigger PITA than mixing, if fact mixing it yourself is quite simple.
TJ is a 10.5 quart system. That means 5.25 quarts water and 5.25 quarts antifreeze for 50/50. After flushing, put 5.25 quarts of antifreeze in the radiator, top off with water. Turn the engine on with the radiator cap off, let the engine get to temp so the thermostat opens, then continue filling with water until it's fully topped off.
That method will not only give you a near perfect mix, it will burp the system of air.