Jim Grant's Tech Tips
Radiator Fluid Mixing, A Big No-No
Q: Can I mix GM Dex Cool with conventional coolant? I have heard that if the two are mixed together they will gum-up.
A: Never mix a long/extended life anti-freeze with what is becoming the old type green anti-freeze. We are seeing a mixing problem not only with GMs long life but with many other manufacturers as well. Not only US but also many of the Asian and European vehicles now specify a long life coolant that is not compatible with commonly known used green anti-freeze. If you mix the different coolants, youre looking for trouble. In the event you do mix the two have the cooling system drained and flushed. It may even take a couple of system flushes to rid the bad mix. In todays vehicles you have to know what youre adding to the cooling system; its not a simple as it use to be.