Well, its really not quite that simple. You see, Dex cool is a formula where you do not have any silicates in the coolant, and it bonds to aluminum and internal parts. Now, the conventional green ethylene glycol bonds differently as well. The reason for this is the chemical composition.
So, even if you flush the coolant out completely, the bonded chemical is still in the metal and other parts of the cooling system.
Remember, even people who attempt a retrofit of the Dexcool to other vehicles, do not really suceed, as the interval will still be 2 yrs 24ooo miles, due to the inability to completely clean the system of the old coolant.
Many people attempt this but the ability of Dexcool to completely work as intended, is the purity of NO other coolant in the system.
Even when asked to do this in a dealer, we cannot perform this, as there is no added benefit.
this is the reasons for my reply.