Thanks for the explanation Mexstan. I took the word undercoating as the black rubber goop. Yout basically saying that the underside is sprayed down with a WD40 type displacement material.

I get it, thanks!

 

Yes. The modern 'undercoating' oil is a special formula and not just ordinary lubricating oil.
BTW, the companies that specialize in this kind of rust protection drill a series of 1/2" holes in strategic places in the vehicle and insert long steel pipes with special nozzles at the end to spray this oil in at high pressure so that it has the chance to reach all the hidden places. Afterwards they plug these holes with plastic plugs. I have had numerous vehicles done this way and it does not detract from the appearance of the vehicle. Each year when it is resparayed they just pop these plugs out and install new plugs afterwards.
If this is done annually I have found that it enhances the resale value of the vehicle.

 

spaying motor oil is illeagal here in maine and at a truck stop inspection you may get a fine or so Ive been told
so I mix 1/2 boiled linseed oil and 1/2 marvelous mistery oil and apply it with a air spayer. I wash and wax my truck the day before and drive some to dry the undercarrige.I make sure to put a thin coat on every thing and wipe the truck down after I'm done .

 

Motor oil I can see as being illegal, but it may be worth your while to check and see if the proper rust preventive oil comes under this category.
Boiled linseed oil is an old time rust preventive and works very well. As far as I know it is still used to coat the interior of chrom moly tubing when used on aircraft structures.

 

I've never really been concerned with the legality of the whole thing. All I know is that spraying plain old used motor oil thinned with a little kerosene has never caused me any problems and I have never had any rust on any of my cars over the past 20 years. So I guess I wont be changing my habits.

 

Have any of you guys used Rust Check to spray your trucks? I pick it up at
Canadian Tire whenever I visit my budy in Ontario. It comes in an aerosol
type can and when sprayed on goes on like a foam and melts away into all
the nooks and cranys to keep rust away. It's red in color and smells sort of
fruity. I used it twice a year on my old Buick LeSabre. They are prone to
rusting around the shock towers where they spot weld plated on. The
car is and 87 with 246,000 miles on it and no rust under the hood. I should
have done the headliner as the stinking winshield is rusting out of it from
the inside My Dodge will be getting the same treatment.
Rob
01.5 3500 CTD

 

This is how I did my old truck, truck was from Oklahoma, nice and clean, and so I sprayed it with POR15 and finished black john dear paint
POR15 is like 135 $ for one gallon but comparing to oil coating you do it once and you good for long time

 

I live in Ontario and have been using Rust Check or Krown for years, very satisfied customer. Krown claims its product is "environmentally-friendly".

Used motor oil? I've heard that it's acidic and not necessarily a good idea to spray under your car or truck, but to each his own. There's also a bit of an environmental issue as that used oil will wash away and wind up on the roads, in the ditches, etc.

POR 15: great job doing your truck! Be wary for places where the POR-15 may flake off, it's been known to do that even when taking care to prepare the surface really well.

 

Fluid Film is my weapon of choice against rust.

Gallons of it can be found online relatively cheap, because a little goes a long way.

http://www.fluid-film.com/

 

You jest, but I will vouch for it- my truck is rust free underneath! Water doesn't have a chance.

 

I have used oil spray for years. I think of it this way, it may cost $100 a year, but the value of the vehicle 10 years from now will be more than $1,000 higher being rust free.
I go to a local guy that works out of his house and charges less, but uses a Petro-Canada product specifically formulated for undercoating.

 

My 91 Toyota had some sort of cosmoline like stuff all over the undercarriage. I didn't pay for it, the truck just came that way.

When I sold it it had over 150 K on it and much of it winter driving. It didn't have any rust under it and after a good washing it still looked new.

Is this what you guys are talking about?

 

No.
Oil, one specifically formulated for this purpose (usually called no drip), or if you're cheap, used motor oil, sprayed annually.
This spray runs into all crevices, displacing moisture.
This also has the advantage of covering any existing rust, to prevent moisture causing further oxidization.

 

MK4288, I'm in your camp also! I don't know why you said just kidding, but the front end of my truck is rust free. I do the back end with Fluid Film also.
Fluid Film rules!

 

Stuff is awesome! I love this thread. DIY rust fighters! Cool!