Take a look at viewtopic.php?f=5&t=56486&hilit=citric . The owner's manuals and FSMs are inconsistent on the cooling system fluid capacity and I don't know that anyone has posted simple a DYI flush that fully cleans the system, I have my own personal opinion on how to do it but since I've not put that into practice I'm keeping that opinion to myself. The underlying problem is that a simple cooling fluid drain leaves a large but uncertain amount of fluid in the system.

What I can tell you for certain is the not simple flush that I had stoutdog use. The short version is to drain the system and refill with clean water; do a brief drive; repeat about 7 or 8 times which pretty much results in removal of all the old or incorrect antifreeze at least by color of the fluid. Once that's done do a final drain and refill with 6qts of full strength Xerex G-05 or equivalent and top off with plain water to reach a 50/50 water/antifreeze mix.