I watched a few videos online regarding how to change the FL-22 coolant in a CX-5, and not one of them showed anything more than draining the fluid from the radiator, then refilling the radiator with water to sort of flush it out, running the engine to temperature, and draining it again, repeating that process twice. A few sites even recommended not power flushing the system, so I decided to just change the coolant myself.

I then did exactly that, refilling it twice, but only 4 quarts of coolant were drained each time, After adding a gallon of the pre-mixed Mazda FL-22 coolant to top it off, I then noticed that the manual says that the total capacity is 8 quarts! Therefore, every time I refilled the system, I was diluting the coolant that remained in the engine (about 4 quarts of fluid).

Doing the math,assuming a 50/50 mix of coolant and water and perfect mixing of water and coolant, the first time I drained the radiator, I left 4 quarts of 50% coolant/50% water (i.e., 2 quarts of each) in the engine. After refiling it with 4 quarts of water, I then had 2 quarts of coolant and 6 quarts of water. Repeating this process, I was down to 1 quart of coolant and 7 quarts of water. Finally, draining the radiator and adding 4 quarts of the correct 50/50 mix, I now have 2.5 quarts of coolant and 5.5 quarts of water, or a 31% coolant/69% quarts of water mix.

Since I live in Wisconsin and air temperatures (not the wind chill) can range from -20 F to 100 F, I'm concerned that this will not be sufficient. Should I be concerned? Is there anyting I can do, short of taking it to a garage and having them do a vacuum flush? The FL-22 only comes premixed, so I can't take out some of the current mixture and add pure coolant.