[Richard]

That designation does not mean anything to me.

In my view of the world, changing the coolant is one of those items that you just do to zero baseline the coach when you don’t have any history.

It’s not a hard project nor terribly expensive. The system is going to hold somewhere between 15 and 20 gallons of coolant. So you will need four five gallon pails to catch the used coolant. You will find a low point drain at the bottom of the radiator closest to the rear of the coach. You will have to look carefully but it is there. Newell made a small hole in the floor below the radiator for access. Your local recycling center should take the used coolant. You may also find a low point drain, on the chromed pipe connecting to the water pump.

Remove the coolant filter when the system is drained. Replace it with a new one. If using the OAT system, then the filter should NOT contain any supplemental SCA additives.

Fill the system with distilled water and bring the system up to temperature. While the engine is coming up to temp, keep the cap off the upper tank and continue adding distilled water each time the level drops. Each time the thermostat opens the cooling system will take a bit more. Turn on the dash heat to high to aid circulation in the loop to the front. Turn on the engine preheat to aid in circulation to the Aquahot.

Drain the distilled water and send it to recycling also since it will contain ethylene glycol.

Now you are set to fill the system with the new coolant using the same technique as the distilled water. If you are a gadget guy, @skyking, has a nifty tool for aiding in eliminating air in the system. https://www.amazon.com/UView-550500INT-A...e904010ad0

This is a day project with modest expense compared to the consequences of mixing coolants or running the engine with exhausted corrosion and cavitation prevention.

And as you are experiencing, document the type and date of change for the next owner.