Our motorhome takes about a gallon and a half. Bought 2 gallons of the -75º pink stuff at Menards for about $4.50/gallon.
I always drain the system first but every year I'm amazed when I see how much water is pushed out of the system when I pump in the pink stuff. I don't trust using just air to winterize, too many low spots.
$9 bucks to protect the plumbing seems like a bargain and cheap insurance to me.
Burns & Diane
2005 Winnebago Aspect 26A/2012 Subaru Impreza toad
Illinois! - Where the politicians make the license plates......