Mushroom - Portabelo or Shitake? .. here is my two cents ... duo centavalo. A friend of mine followed the manual and blew out the lines according to the owners manual of his 2002 Journey. He used no antifreeze except in the traps. That resulted in a cracked frozin line beneath the shower or someplace in that vacinity. Cost ... mucho denearo to have the dealer fix.
As far as econimics .. RV antifreezethe is the least expensive item you will buy for the rig to keep your lines from freezing. In the north east, RV antifreeze from a boat delaer is about $3.50 a gallon.
I use four gallons and end up with some left over. Lots of insurance for $14.00. I happen to have a siphon line at the intake side of my pump so all that is required is opening and closing the necessary valves, draining the fresh water tank, draining the water heater, by passing the water heater, disconnecting the ice cube tray feed, and using the pump to drain the lines to all the faucets. I then place the gallon or two onto the siphon feed tube and open each faucet till I see pink. About two cups of anti freeze in each trap a gallon in the black and a gallon in the gray tanks plus the recommended odor fighting chemicals and I am done. It is recommended to leave the toilet open to the black tank.
Knock on wood .. or is it now fiberglass .. in any event, I've not had a problem.
good luck... Frank
2001 Adventurer 32V