New to me 1992 fleetwood 454 motorhome coolant question

Sep 4, 2021
Motorhome in question has the 454 BB TBI engine and I wanna change out the coolant as I don't know what's in it or when it was last serviced. What coolant would this take? Live in Las Vegas so hills and Summer heat play a role. No freezing Temps but winters tend to get chilly
Prestone all vehicle concentrate from WalMart is a darn good choice and likely the best price too. Make sure to flush out the system before adding a diluted 50-50 mixture.

As always, the more antifreeze in the mixture, the lower the freeze point and the (slightly) higher the boiling point. Note: Boiling point is mostly controlled by the pressure cap rating.

But remember, water transfers heat best, so in things like race cars and hard working vehicles with marginal cooling systems, it may be slightly beneficial to move away from a 50-50 mix. A 60% water, 40% coolant mix is not much risk, as it will still protect the water pump and provide good freeze protection.

Here in South Florida, it is not unusual for me to use 70% water and 30% Prestone in my modified turbocharged engines.
Another reason for using the Prestone concentrate is that it is commonly available at every WalMart and elsewhere. If you need to add some when on the road, it is easy to get the exact same product.
You could go with any modern coolant. I personally would select one of the new long life coolants, like Prestone Max All Vehicles or Zerex Green or Zerex Dex-Cool. Considering that it is going in a motorhome, and the engine may be working hard, and If you want a more heavy duty coolant, I would recommend Zerex Heavy Duty Extended Life. It meets most all the specs for diesel engines, and is formulated for 300k mile life.

The important part is, as @Cujet mentioned, to do a very thorough flush. If you do that, you don't have to be concerned about compatibility with the old, unknown coolant that is in there now.