If your black and gray tanks have just a little water in them, it will not cause any problems if they freeze. But, it doesn't hurt to add some RV antifreeze if you're worried about it.
For winter storage, it's a good idea to set some rodent traps and check them periodically during storage. And....mice love bullion cubes.....don't ask me how I know. So, removing all food is a good idea.
Don't forget to follow guidelines for exercising the generator i.e. running it once a month with a load.
Retired but busier than ever!
2012 Newmar Bay Star 3302
5 Star Tune, SumoSprings, Roadmaster Steering Stabilizer, Blue Ox Avail
Brake Buddy, 2015 Chevy Malibu