Hooniverse Asks: Oil Undercoating?


I own a Toyota. One issue with Toyotas is that Toyotas seem to rust at an accelerated rate. I happen to live in New England where sometimes we have more salt on the ground than snow. I recently took a gander underneath my 50,000 mile rig and almost regurgitated my muffin and coffee. It looked bad but it didn’t seem structural. Like so many Craigslist ads say, surface rust only. Still, I’m not feeling good about that. 
I have heard some positive things about oil-based undercoating. It’s gets sprayed on and protects the chassis. It’s not permanent, needs annual re-do’s, but doesn’t damage anything no matter where it is sprayed. But most of this came from the companies that do this sort of thing and not from the vehicle owners. Has anyone done this? If so, what were the results? Thanks. 
Image: Oil Undercoating of NH INC

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52 responses to “Hooniverse Asks: Oil Undercoating?”

  1. GTXcellent Avatar
    GTXcellent

    For the first time, I’m trying this on the Rubicon for the winter
    https://images-na.ssl-images-amazon.com/images/I/41DtoLsGG7L.jpg
    $4 a can, took 3 cans. Goes on clear, doesn’t harm electical, rubber, etc. Has to be better than doing nothing.

  2. Sjalabais Avatar
    Sjalabais

    I’m not a big fan of this approach. Annual redos sounds ok until you realize how fast a year rolls over. In our area, driving on gravel or snow/ice roads that bombard the car with sharp stuff, oil treatments wear off relatively quickly and unevenly. Even though it is recommended to take a drive on gravel after an oil treatment, for that fine layer of protective dust™.
    Our Honda got a Mercasol-treatment, the Toyota is up for Tectyl-renewal in three weeks. This is expensive (Honda 800$, Toyota 1200$) and you have to trust your shop to do it right – get off existing rust, dry it well/don’t lock in moisture, be thorough with getting in everywhere. I contemplated doing this myself once, but figured I’d do more damage than good.
    A cheap alternative to mineral oil treatments is lanolin oils. They are eco-friendly, supposedly last a little longer, are extremely well-suited to creeping in everywhere, and it is a cheap, simple procedure. The biggest downside is that your car smells like a sheep stew for weeks.

    1. anonymic Avatar
      anonymic

      What’s a better alternative? Ziebart? Just take it out and shoot it if you’re putting that crap on your car.

    2. Smaglik Avatar
      Smaglik

      Sheep stew…does that result in predators stalking the vehicle?

      1. Vairship Avatar
        Vairship

        Whatever makes you say that? https://uploads.disquscdn.com/images/c1134251f8d02bf48056ecba9fb4feacafb76ece411132e6657e508356443fa2.jpg By the way, we have a flat tire. Be a lamb and go change it please…

  3. P161911 Avatar
    P161911

    I have had several vehicles with an oil under coating. I usually used 10W-30, but occasionally ATF or power steering fluid too. Of course this oil just came from leaks. I live in Georgia, rust isn’t really an issue here.

  4. Mitch Horner Avatar
    Mitch Horner

    Learned from the Clevland Moto guys, they swear by Fluid Film. I have been applying it to my 3rd gen 4runner frame and it seems to have slowed the rusting. I apply once before the first snow fall.

  5. Tracey S Avatar
    Tracey S

    I bought a 68 Ford wagon back in the day from a retired Streets and San worker in my town (we live in central IL). The underside was IMMACULATE and I asked how it was kept that way. He let me in on his secret of coating all his cars in linseed oil , underneath-any seams-anywhere that dirt and water can collect.

  6. mdharrell Avatar

    “…but doesn’t damage anything no matter where it is sprayed.”
    As the owner of belt-driven vehicles which only stand a chance of working so long as their exposed belts and split pulleys remain clean and oil-free, I question this claim.

    1. anonymic Avatar
      anonymic

      So is it the oil that’s damaging the belts or is it neglecting to keep the belts clean and the slippage and accompanying heat that damages them? Oil doesn’t hurt rubber, or they wouldn’t make oil seals out of the stuff.

      1. Rover 1 Avatar
        Rover 1

        Oil does hurt rubber, it is absorbed and makes the rubber swell.
        It’s why engine and gearbox mounts fail after a bad oil leak.
        Oil seals take advantage of this fact to stay supple, and use additives to the rubber to control the swelling. The use of silicon, as an additive, has come on in the last thirty years, partly due to this… https://patents.google.com/patent/US5010137

      2. mdharrell Avatar

        My understanding is the immediate concerns arise from slippage and its consequences, although as Rover 1 noted the belt material itself will deteriorate from prolonged exposure. I’ve never been keen to find out for myself, as the belts are rather a pain to replace.

        1. anonymic Avatar
          anonymic

          Regardless, it’s still neglect on the operator’s part. If your drive system is a belt, and you lubricate it and it fails, it’s not the oil’s fault. It’s quite stupid to claim otherwise.

          1. Zentropy Avatar
            Zentropy

            I think mdharrell’s issue was with the claim of no damage regardless where the oil is sprayed. Anyone using this method of undercoating for rust prevention therefore can’t be careless with application.

    2. Vairship Avatar
      Vairship

      Make sure to always carry some spare garter belts, no matter the weird looks you get 😉

      1. mdharrell Avatar

        Good point. I should probably put those in the car.

  7. Alff Avatar
    Alff

    I think I’d go with POR15 instead. Similar amount of labor, longer lasting results.

    1. dead_elvis, inc. Avatar
      dead_elvis, inc.

      And that (or something similar) appears to be the treatment of the frame pictured at the top. Or maybe advances in oil-undercoating procedure now treat bed removal as standard.
      Beats me, my folks never had a pickup when I was a kid, but used motor oil undercoating was de riguer for their cars from the early 70s until at least the late 1980s, and seemed to work rather well in Vermont – never anything more than surface rust on the cars they owned while I was growing up.

      1. Alff Avatar
        Alff

        Undercoatings should be applied over clean, rust free and generally painted surfaces, lest they trap and promote corrosion. The pic above may illustrate the results of that prep work.

        1. dead_elvis, inc. Avatar
          dead_elvis, inc.

          Sorry, neither enough sleep nor enough coffee (yet) & my attempt at snark fell flat.
          Dad’s 02 Tacoma didn’t qualify for a full frame replacement, but for this sort of treatment, and it worked poorly. Bad prep or execution? I don’t know, but Toyota refused to make it right, and the local Toyota dealership wasn’t willing to assist in any way.

          1. anonymic Avatar
            anonymic

            If it was a black undercoating, it wasn’t oil, it was rubberized undercoating like the truck pictured above.

          2. dead_elvis, inc. Avatar
            dead_elvis, inc.

            Yes, and ?

        2. nanoop Avatar

          This.

    2. Vairship Avatar
      Vairship

      Right, if I had to go to all the trouble the guy in the lead picture went to (bed removal), why then use lousy motor oil instead of zinc-based primer and a good paint system? The cost savings of used motor oil (with all the included acids) really aren’t worth it after all that labor.

      1. Alff Avatar
        Alff

        If that is the photo that these snake oil salesmen are using to promote their product, they are full of shit.

  8. mike Avatar
    mike

    Kamil – Its a Toyota. Frame’s destined to rust and crack in half regardless of what you try.

  9. Windbüchse Avatar
    Windbüchse

    My Jags always had a self-administered undercoating of engine and transmission oil. Didn’t stop the tin worm though….

    1. Rover 1 Avatar
      Rover 1

      Also shared with Rover SD1, P6, P5, P4, etc and Trumphs.
      All British and many French and Italian cars too. My Lancia Gamma has paper gaskets in parts of the engine.

      1. Windbüchse Avatar
        Windbüchse

        Greetings Gnomical, the oily surfaces were somewhat protected. The problem areas were inside the box sections, ie. corroded inside out. Also, the oil would crust over with dirt, leaving areas that would trap water and mud, sometimes clogging drain holes. Living in SoCal is not a litmus test for rust proofing however….

  10. Peter Tanshanomi Avatar

    Am I correct in assuming that this is a particularly Northeast/New England thing? I had never heard of this until the guys on the Auto Off Topic podcast discussed it. Frankly, it seems super strange and sketchy to me. I can’t imagine how dousing the underside of your vehicle with a liquid that will immediately start dripping off is the most effective, tidy, or ecologically sound way to deal with the problem of corrosion.

    1. anonymic Avatar
      anonymic

      So covering metal with oil doesn’t seem like it would protect it from corrosion to you?

      1. Peter Tanshanomi Avatar

        Not indefinitely, especially outside, in the winter, on a moving vehicle.

    2. dead_elvis, inc. Avatar
      dead_elvis, inc.

      Maybe it’s a cheapskate thing – the guy that treated my folks’ cars in the 1970s & 80s used spent oil from trucks & tractors that didn’t make it into the fuel tank for the oil burner that heated his shop. SOP was to then spend a few miles on the dustiest dirt roads you could find, immediately post-treatment, in order to encapsulate the freshly sprayed oil. (So, don’t wait until Halloween to do it, or you’ll be SOL finding dusty roads in the NE.)
      I’m old enough to remember when some old timers who’d been making maple syrup forever still burned old tires to fire the sugar house evaporator, instead of using firewood. No cost to throw out old tires, AND boiling down maple sap into syrup? Win-win, from a tighwad Yankee perspective.

      1. Sjalabais Avatar
        Sjalabais

        Some old Norwegian forest barns still carry their used motoroil “paint” with pride. It protects the wood really well, and it gets shiny and sticky still even though the last painting process might be three decades ago.

  11. SlowJoeCrow Avatar
    SlowJoeCrow

    Spraying used oil on the underside was a common thing in Upstate New York back in the day but there are more effective and less toxic options these days. The English swear by Waxoyl and I think that or similar products are available in the US. Of course you do need to apply undercoating to clean dry, and rust free metal or you just seal the rust in and create a structural time bomb.

    1. Ol' Shel' Avatar
      Ol’ Shel’

      Rust is steel+moisture. If moisture is getting through the coating, it won’t matter if there’s rust beneath or not.
      Sure, don’t spray over flaking rust, but treatment over light surface oxidation is fine.

  12. Maymar Avatar
    Maymar

    I’ve never done it myself (I really should, considering I own a Mazda in a wintery climate), but the one concern I’ve heard of is that some shops may drill in places (to spray in), and fill the hole with a rubber grommet. I’m all for spraying anything accessible, but drilling is probably a step too far.

  13. anonymic Avatar
    anonymic

    1000% better for your car than Ziebart or any other rubberized undercoating. The oil base stays malleable and conforms to the surface of the parts it is sprayed on. It’s difficult to remove and it’s very thin, so if for some reason it is failing, it would be apparent immediately. Think of it as thick WD-40 Chances of actual failure: near 0%.
    Rubberized undercoating (the black crap on the Ford above) on the other hand is rigid, traps moisture underneath the coating and rots your car to pieces from the inside out. Basically, it’s thick goopy paint that makes the damage it is doing to your car look great from the outside. Chances of failure: 100%. Your car would probably rust slower if you parked it in the ocean. Check out a video by South Main Auto on Youtube: https://youtu.be/nXvl9nt57Kg. If you don’t watch SMA, you should.

  14. I_Borgward Avatar
    I_Borgward

    Back when I lived in the Great Lakes area, it was common to get a car treated with rustproofing grease. If you did it properly, it would definitely slow down the rot. It would spray on as viscous goop, then dry out over a few weeks. I recall my Dad having the tech squirt a container full of the stuff from one job so he could take some home to reapply if needed. Far, far and away better than the rubberized crap, which, as mentioned above, can be worse than useless.
    Working around the stuff could be messy, though. Sometimes you’d have to dissolve it off of fasteners before you could put a wrench on them. But, you’d usually find a nice clean bolt head underneath. Another thing you had to watch for was keeping the factory drain ports cleared; if they overdid the grease, they could get plugged up and trap water.
    Motor oil, used or not, is nasty, nasty stuff to use for undercoating. You don’t want to breathe the vapors from spraying, smell the stink on your car or pollute the environment with it. Just because Gramps used to hose 10W30 all over his F150 doesn’t make it a good idea.

    1. mdharrell Avatar

      Oh, please. I’ll have you know neither of my grandfathers ever would have had anything to do with multi-viscosity oils.

      1. I_Borgward Avatar
        I_Borgward

        Same here, now that I’ve really thought about it.

  15. MattC Avatar
    MattC

    I had an older Ford Ranger (originally from Maine). Thankfully the frame only had surface rust. I used a wire brush, slapped Corroseal (spelling?) on the frame. After letting it dry for 24 hours, I painted it with chassis black paint. I plan on doing that for my newer 2010 Ranger. Better to address it early then wait for more serious rust to occur

  16. LeaksOil Avatar
    LeaksOil

    Being a life long southerner,… this is all new to me. Never seen or heard of any such thing.
    Interesting.

      1. LeaksOil Avatar
        LeaksOil

        I’ve almost always lived within a couple hours or less of the Atlantic coast. And lived in Savannah, GA on the coast for a year. Still never seen or heard of oil coating.

  17. Ol' Shel' Avatar
    Ol’ Shel’

    Kano Labs makes great chemicals, and their literature seems to be unchanged from the 1950s (lubes that are perfect for typewriters!) They also misspell everything, like Weatherpruf. Buy a gallon and a spray bottle, and start spraying. It’s doing a great job protecting my belongings.
    https://websecure.cnchost.com/kanolabs.com/orders/order_weatrial.shtml