[ImperialCrown]

Yes there was a change from HOAT to OAT. Is this label on your recovery bottle (see link)?
When in doubt, flush completely.
http://www.sae.org/mags/aei/11284

 

[ImperialCrown]

Yes, they are incompatible with each other.
If you haven't already, get a complete flush until it runs clear. Then refill it with OAT.
I have had vehicles come in overheating with jelled coolant and it isn't good, especially for aluminum engines to cook.