We're lucky enough to live on the central coast of California, so we don't have a ton of winterizing experience. I mean, let's face it: in the middle of January, we're likely to have 72 degree weather and clear blue skies. Oh, wait... I probably shouldn't say that. What I meant to say was, "It's always foggy and rainy and cold and miserable around here."
For you folks that live through cold-weather winters, winterizing your beloved VW is very, very important. Here are a few basic tips to get you started, but be sure to consult your local RV shop to see what type of winterizing techniques they advise.
Fuel: When your vehicle sits for a long period of time, the gasoline in the tank tends to get gummy—this is often referred to as "stale fuel." However, if you're only planning to hibernate your VW for 4-5 months, there's no need to add a fuel stabilizer. Fuel doesn't tend to destabilize until it sits for a year or so. Still, some people are convinced that adding fuel stabilizer is important for wintertime storage. Check with your local parts shop to see what they recommend.
Battery: First, make sure the vehicle is stored in a warm, dry place. That's how batteries like to be stored. We recommend just disconnecting the ground, although in some cases it's a good idea to keep the battery on a charger (one that has a "maintenance" setting). If you've got a camper, remember to disconnect the auxiliary battery, as well! Further info can be found here.
Rodents: There's nothing worse than opening up your camper for the spring... and finding that you've had some unwelcome tenants living there all winter long. The kind of tenants that leave, um, surprises for you to clean up. Yuck. So, before you tuck your vehicle away for the winter, make sure it is clean and tidy. Don't leave food stored in there. That's just asking for trouble. Some folks use mothballs, as most rodents won't get near those nasty things. Also, if you've got a full camper Westy, you can shove some coarse steel wool in the breather-to-battery compartment(s). That's a common entry point for those buggers.
Fresh water tank: If you've got a full camper, we definitely recommend draining your fresh water tank. Some folks forget about this small detail, the cold weather hits, the water in their tank freezes, and the water pump goes kaput.
As a side note, it's worth storing your vehicle clean and dry. Make sure any dirt and grime is cleaned away, and you won't have to worry as much about rust developing. This is especially important if you plan on covering your vehicle. Never cover a dirty vehicle.
When springtime comes and the snow melts away, get in that thing and drive with confidence. You're taken good care of your vehicle, and now it'll take good care of you. Be sure to air up the tires, and then hit the road!