I'ld say regardless if they mixed or not, you would need a flush. I don't think the white chunky stuff is from them mixing OAT and HOAT. The white chunky stuff is usually caused by some kind of air leak within the cooling system. I say this based upon past experience where my wife had a 2003 Jeep Liberty and I took it into an oil shop and they said I needed a coolant flush and showed me the same looking white chunky stuff. I got the flush done and 2 years later I had white chunky stuff again, where it was then explained to me that the white chunky stuff is usually an indication that there is a small air leak within the cooling system.

 

Thank you. Unfortunately it's brown sludge. Could this also be because of an air leak?

 

This is what mixing does......

 

Still waiting for a call back from the dealer. Mine isn't quite that bad bud there is still sludge everywhere. Hoping they take care of it because they admitted to putting the wrong coolant in.