LEt's see some pictures of the doors.
When I got my 04 (gently used, never saw winter in until '09) I coated the door skins (where it's folded over inside) with lithium grease.
Fluid Film claims to starve off rust. I've also heard of a quality bar & chain lube being used as a rust proofing. Heavy tar will only trap the corrosion at this point and cause it to continue to fester.
Let's put it this way, even if we had KROWN from Canada, their requirement is to have the car washed once a week with a clean (not recycled) car wash.
I found that CRC Heavy Duty Corrosion inhibitor holds up the best.
IF you wash the car yourself, use Salt Away. Does a great job cleaning and supposedly protecting. I've used it for one winter now.
Cortec VpCI-368D
Valuegaurd is good stuff for summertime washings
Detail Wash
Here's rust proof testing
http://www.cortecvci.com/Publications/Reports/06-192-1125.pdf
Oil undercoating - Page 4 - Toyota FJ Cruiser Forum
Oiling the under carriage
This gets into the alkalinity of soap
Rust Never Sleeps - 1130cc.com: The #1 Harley Davidson V-Rod Forum
I've used this before: Salt Away:
Salt-Away's Car, Truck, Motor Home Applications ...
Some blank metal testing...never tested against fluid film though...FF claims to beat it.
Competitiom
Make your own:
from this source:
TIPS AND RECIPES
WAXOYL
Take a ½ kilogram of paraffin wax or candle making wax and grind it up with a cheese grater. Soak it in 2 liters of mineral spirits/ Paraffin/ Kerosene/ lamp oil/ Diesel until all of the wax is dissolved. It might take a couple of weeks. Stirring will cause most of the wax to dissolve, but soaking should take care of the rest, heating the mixture in hot water (no open flames) will add in the quick dissolving of the wax. Generally try to dissolve as much wax as the mineral spirits/ kerosene/ paraffin/lamp oil/ Diesel will hold. Pour one liter of mineral oil/ non-detergent motor oil into the dissolved mixture. If the mixture is too thick for spraying you can thin it further with more mineral spirits until it is of a spray-able consistency.
Application:
Buy any cheap engine spray gun at your local auto or tool store that carries air tools. You can also use a garden insecticide sprayer, although it will really make you tired. Rent or borrow an air compressor. If possible elevate your car so that you can get at the underside. (Remember to chock both front and rear wheels as you are going to work underneath the car.) First wash your truck's chassis, both inside and out, to get rid of all the mud, oil etc. Spray the solution onto the underside of the chassis and into every little hole, crack and crevice. Make sure you push the tip into the chassis to spray the inside of the chassis. Let the excess drip off. You will find that the solution will blend into all cracks and chips and if the chassis is scratched it will flow, covering the scratch. If there is existing rust the solution will be soaked up by the rust and thereby creating an oxygen free coating stopping the further rusting/corroding of the surface.
Repeat the above once a year if you live in an area where the roads are sprayed with salt. Once every two to three years if staying inland where it is dry and salt free.
The above information was received from the LRO list where various people contributed their own recipe. Most of the recipes was essentially the same varying only on which oil to use and discussing the pro's and con's of Mineral spirits/paraffin/ Kerosene/ lamp oil vs. Diesel etc.
Here is a recipe for home made "Waxoyl". It's an old fashioned rust treatment / undercoating:
2 1/2 quarts turpentine
12 oz. beeswax / candle wax
1 quart light machine oil
With a cheese shredder, cut the wax into the turpentine, stir until the wax has dissolved, (takes a long time; you can use very low heat (a warm room) to aid but be careful) and thin with the machine oil to a brushable / sprayable consistency. Apply liberally. You can use a hand spray bottle to get into closed-off sections if you have a small access hole.
Please be sensible when you make this stuff; don't go breathing the fumes or applying heat and burning down your house. If you have any doubts about it, err on the side of caution and just buy a commercially available product.
I personally like using a paintable undercoating covered with fluid film. Paintable undercoating goes on very thin, but maintains a nice skin and fluid film helps to seep through the UC and add a second layer of protection from rust through.
