OH GREAT, I PUT SOME ORANGE IN MY CAR!!!!!
Q: Can I mix green coolant with orange coolant?
This is one of those questions usually asked after the fact, and usually engine damage has already occurred. The green and orange coolants do not mix. When mixed together they form a gel-like substance that stops coolant flow and consequently the engine overheats.
There are some coolants that claim compatibility with Dexcool, but I would rather err conservatively and add what the system is supposed to take rather than gamble. To guard against major engine failure, read on.
What exactly happens when these coolants are mixed?
The coolants chemically react and form a gel rather than a liquid. The coolant stops flowing through the system, clogs up coolant passageways and water jackets, radiators, and heater cores. The water pump overheats and fails due to a lack of lubricant in the coolant. Head gaskets blow, heads warp, and the engine suffers major damage.