By on February 8, 2010

Karl writes:

Sajeev, I am not sure if this has been covered before, but I am writing about washing cars in winter. I finally have a car that is new enough and nice to worry about keeping the body in good shape for a long time. It will not be driven that regularly, so I expect to keep it for a decade–I tend to keep my cars a long time. I remember reading long ago (okay, long, long ago) about not washing vehicles in freezing weather. Well, I live in Wisconsin, so that is a third of the year. I want my new purchase to last, so what should I do to preserve the paint and the body?

Sajeev answers:

I’ve spent most of my life in the Texas Gulf Coast, so I shouldn’t answer this question.  But with the (thankless) hours spent as an automotive forum moderator, I shall.  There’s always a thread on preserving sheetmetal in the Rust Belt: I’ll share what I’ve heard from intelligent forum contributors.

I recommend washing a car in the winter, especially if it’s done weekly and using a proper underbody wash to keep road salt off your ride. I’d also polish the car with a polymer-based wax to protect the paint the entire season. Then grab some mudflaps and get ready for the big chill.

Most importantly, don’t let the car thaw in a heated garage every day.  The logic says that a car with salty ice in every orifice protects itself better than one that turns into salt water every evening, permeating into every poorly protected sheetmetal crease.  I’ve heard (keyword: heard) of cars that live completely rust free with a strict regiment of living outside during winter, with a heavy coat of “water” from the owner so it can completely seal the drainage gutters and door seams as it freezes.

Makes sense: I’d soak every non-moving part in water and let Mother Nature protect my ride from the government’s evil, evil salt fixation. Which is definitely easier on the environment than the toxic chemicals in automotive undercoating. And that’s far cheaper too.

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34 Comments on “Piston Slap: Fight Rust With Mother Nature?...”

  • avatar

    I’ve heard (keyword: heard) of cars that live completely rust free with a strict regiment of living outside during winter

    This is true. In areas that salt rather than sand, you’re asking for a world of hurt if you park indoors. Let the car freeze, and let the salt accumulate as long as your car is pre-undercoated and has no bare-metal spots exposed

    I would also recommend:
    * washing and undercoating only when the temperature creeps nearer to zero celsius.
    * get undercoated yearly, usually just before winter.
    * even better, go somewhere for a full anti-corrosion treatment. In southern Ontario (aka: The Land Of Salt), this means Krown: they’ll make a point of getting at the drain holes, sills and suchlike where saltwater pools. They’ll also stand behind their work.
    * wax the car with the intent of protecting the paint. This means a nasty, thick, ugly waxing, not a show-car sheen.
    * repair any metal-panel body damage (hugely important!)
    * get a hood edge deflector, if you don’t already have one
    * keep an eye on your wheel wells, door sills and strut towers. If it’s going to start, it’ll start there

    • 0 avatar

      “Go somewhere for a full anti-corrosion treatment. In southern Ontario (aka: The Land Of Salt), this means Krown: they’ll make a point of getting at the drain holes, sills and suchlike where saltwater pools. They’ll also stand behind their work.”

      Hmmm — interesting idea!

    • 0 avatar

      This might work in Ontario, but on the other side of Great Lakes it never gets cold enough for the salted snow/mud to freeze on the car undercarriage. Even if you leave it outside overnight and it freezes, chances are the temperature during the day would creep in upper twentieth (just below freezing) and the salted icicle would turn into a mess corroding your car.

  • avatar

    Also, if you wash it, try not to use a commercial car wash power wand on the body as it will strip the wax as will hot water. If at all possible hand wash the body with mildly warm water in a heated space

  • avatar

    Sajeev – since you wouldn’t be here if you hadn’t been there (thankless job) -> Thanks . . .

    I hadn’t heard about rusting during nightly thaw . . . that, well, sucks. I assume that’s more of a danger with the higher the salt content/coverage/caking?


    • 0 avatar

      Thank you. I definitely wouldn’t have the stones to answer these questions without 10+ years experience as a Forum Moderator. And it wasn’t totally thankless, but we Moderators get the short end of the stick from other members. All to frequently.

  • avatar

    Don’t overthink this. If you want the car to last only a decade you could simply do nothing other than occasional rinses during the winter and a good wash in the spring. Wipe down the door/trunk sills/seals and keep the drains clear. That’s it. Believe me, I had a couple of Toyotas in the 80s that easily survived a decade of New England salted winters this way. Sure, there were small rust spots, but today’s steel and construction is far superior in general.

  • avatar

    Modern cars with galvanized sheet metal don’t have rust issues any more. In Michigan, there are lots of 15 year old cars limping along with absolutely no rust on the body. My 19 year old Caprice, with 450,000 miles and lots of winters, living outdoors the whole time, didn’t show a speck of rust when I gave it away last fall.

    I had dinner with a paint engineer from one of the largest paint suppliers. He stated, unequivocally, that there should be no degradation of the paint on a modern car for at least 10 years, with no waxing whatsoever. We looked out the restaurant window, in Detroit, and could see 2 15 year old cars with perfect paint.

    I wouldn’t worry about rust.


    • 0 avatar
      IC Turbo

      Tell that to the 1995 Taurus I had that lived most of its life in Rochester, NY. Weather is similar to Detroit area, maybe with more snow. The hood and trunk lips were rusted to the point that the license plate light was only held in place by its wiring. There was also visible bubbles in other spots. The car only had 105k miles on it. Don’t even let me get started on the underbody. Every where was flaking rust, exhaust rotted off, fuel tank straps broke from rust, and when the fuel tank started to leak, I sold it so that I wouldn’t have to deal with rust anymore. I disclosed all known issues upon sale.

    • 0 avatar

      Mazda3’s are also prone to rust. I’ve also seen lots of early 2000’s era GM vehicles with body rot around the wheel wells and fuel door.

    • 0 avatar

      My 97 Voyager is doing fine in the slush belt north of Chicago.

    • 0 avatar

      Late model Mazda 3’s, Ford Foci and Mazda 5’s (I think) all had their moment of shame on Piston Slap for shoddy rustproofing. Six Sigma production can’t always get things right, especially after 5+ years of use with the final product. Who actually measures this stuff? (points to TrueDelta)

    • 0 avatar

      “Modern cars with galvanized sheet metal don’t have rust issues any more” Well, it is not true in Sweden and I guess not in the rustbelt in the USA. Also the great Caprices are dissolving here. It seems like many modern car with galvanized bodies does not get much undercoating any more. And when there is a small defect or if the rust get started somewhere, then it is soon over. The only thing that helps are spraying the underside of the car, inside the doors, hood and other cavities with some kind of rust preventing oil. The rust guarantee is void if drilling holes and spraying the car, but many people prefer having a rust free car without a guarantee than vice versa. Once I had a twenty year old SAAB 96 V4 from 1967 treated with used motor oil and no rust issue!!! I guess it would’ve worked also on an Alfasud, but it might be to exhagirate!

    • 0 avatar

      Yes, Mr Elton, I suppose that’s why my friend’s 2003 Grand Caravan AWD last month had to have 3 grands worth of replaced inner panels that were rusted to nothing. It failed our annual vehicle inspection.

      It’s only six years old, not 10 or fifteen. Lots of rust here in Nova Scotia, which is why Honda used to keep a full time facility to study why cars dissolved in our fair Maritime climate. Hondas used to trail bits and pieces of detritus behind them, hanging on by wiring after only three or four years of service.

    • 0 avatar

      IC Turbo, I think Ford had a paint issue in the early 90s. On my 93 Escort the paint in the rain gutters flaked off after a few years, exposing the primer, which eventually rusted. Still got over 200k miles before I sold it, and it’s probably still running.

    • 0 avatar
      IC Turbo


      After having owned a 95 neon, I know what peeling paint problems are. The Taurus had serious rust issues. Not surprisingly, all of the Tauri I pulled parts from here in KY junkyards had significantly better bodies on both the painted part of the bodies and underneath.

  • avatar

    Is that a Toyota MR2 under there?

  • avatar

    Another Canadian endorsing Krown rust preventative here! The worst part about Krown is that I got rid of my used up 1988 Ranger without a speck of rust on it. I disagree that modern cars don’t rust, they certainly wait longer before they start but once they start look out. Safety fanatics take note that rusty cars come apart in crashes, so if you’re going to be keeping it for the long haul it’s essential. Krown FTW!!

    • 0 avatar

      Krown are clowns in my book. I watched in horror as blunt drills tore into my new Impreza back in 1998, leaving holes with sharp shavings and raised lips. The plastic plugs wouldn’t lie flat against those drill holes. I protested at the time, but got blank looks from the idiots running the store.

      Four years later with rust creeping from every hole, I took advantage of Krown’s guarantee and had the damage fixed for free at a body shop of my choice. They did not argue and paid up. Also all the rubber around my sidelights swelled up and hung down. A totally useless product, IMO.

      After 9 years the Impreza had rust just forward of the rear wheel openings, just like every other Impreza of that vintage, after market rust-proofing or not. Krown did squat.

      My new Legacy was not subjected to this patent medicine hoax.

  • avatar

    While paint may last for many years without waxing the appearance is without question much nicer with waxing. Assuming the original poster has a nice enough car to preserve I’m sure they also want it to look as good as is reasonably possible. Using a clay bar prior to a good quality sealant will do the trick the first time and after that resealing twice a year. (use a non wax based paint sealant-lasts much longer than even a high quality wax) Depending on whether an automatic car wash or coin operated is used it’s important to flush out the wheel wheels and undercarriage but if using coin operated don’t use the high pressure setting on the paint, it just drives the dirt into the paint.

  • avatar

    After living in central Massachusetts for a little while, it seems that the normal way of doing things was that when the weather got above freezing, which happened every now and again, to go get you car washed off, with the undercarriage wash being the – obviously- most important part. So, if you do live in a part of the country that a. uses a ton of salt and b. isn’t below freezing for a large portion of the winter, then something like this may be the trick. If you do live somewhere where it is freeing for a while, then I bet the frozen water trick would work well, since it’ll stay in all those cracks and crevices for a while.

  • avatar

    It may well take a regiment to keep salt off your underbody. I lived in Michigan for five years, and salt on the bridges was deep enough to be a hazard even when dry.

  • avatar

    Typical undercoating involves drilling holes on the “sealed” sheetmetal. The metal is coated before paint. It can also “seal in” dirt against the body, leading to additional rust issues.

    Car washes, especially the underbody blast uses recycled DIRTY and SALTY water. Touchless car washes use heavy duty chemicals to overcome the caked on dirt.

    Hood deflectors can change the aero dynamics enough to cause rocks to land on the flat surface of the hood instead of the leading edge. They can also cause wiper issues with the changed aero flow.

    Sorry Sajeev, I normally agree with you, but not this time.

  • avatar

    Have to agree w/ Cardeveloper; Couldn’t afford to run a car wash w/o using recycled water; you can filter out the sand and kuka, but not the salt in solution. Not to mention the municipalities would not let you discharge that volume of untreated runoff into the sewer system.

    Around here we have “Ziebart” rustproofing, they drill holes in the rocker panels and door jambs stick the applicator nozzle in, then plug them with plastic plugs. The drilled holes are where the rust starts.

    They’ve been using so much salt lately, we drive through clouds of salt dust for days after a storm. You’d have to wash your undercarriage after every trip.


  • avatar

    Salt attracts water like crazy, and happily absorbs it out of the air. Salty water freezes at a colder temperature than pure water. So any trace of salt on your car, even at temperatures a few degrees below freezing, will be wet. If it’s wet and on bare metal, it will rust.

    It’s important to flush off alloy wheels, and keep them waxed.

    Primer paint is porous, so you can get rust through primer. Modern water-based paints are water-soluble, even when dry. So you have to touch up paint nicks before they rust, even if the primer is still there. And, you have to cover the body color paint with clear coat, or it will wash off after a while, leaving the primer exposed to rusting.

    I keep cars for 10+ years, and rinse them off top to bottom during the winter, except when it’s so cold the water runoff will freeze and create a hazard on the sidewalk and street. I flush gravel out of the ledges inside and around the wheel wells. I try to flush off the top of the seam around the gas tank, as it will hold salty crud and eventually result in the tank leaking when half full. Lately I’ve been trying to flush off the inner faces of the brakes. Flushing out ledges and box sections on frames is important. When I had cars with steel bumpers, I’d flush out the inner sides of them.

    When I bought older vehicles, I’d get them treated with Krown. Except the Spirit, which inexplicably seems to be rustproof.

    I never ever take cars to automatic car washes. They are death to paint.

  • avatar

    I can’t speak for other areas, but Omaha certainly puts enough salt on the roads and has for decades.

    Cars today are much more rust resistant than they were 30 years ago. We had a late 70s Datsun that showed rust in only two years. Eventually, the wheel wells got to be four inches larger than stock. In contrast, our 1998 Subaru Legacy is just beginning to show some stains on the rocker panels below the leading edges of the front doors.

    Even fifteen years ago, the advice I received from car company engineers was not to get aftermarket rustproofing. At best, it doesn’t help. At worst, they promote rust by drilling holes in the wrong places and/or plugging critical drain holes.

    The only sure way I know to keep a car from rusting is to keep it out of the salt. During the winter, I drive my Infiniti G37 only when the roads are clean and dry. This year, it has been parked since the beginning of December.

    • 0 avatar

      Not only does Ziebart plug drain holes, but the crap gets into your window regulators and render your side windows inoperable.

      I had a 1984 Voyager with manual windows whose former owner Ziebarted it, and not only did the rear quarters rust out, but the door glass took both hands to raise and lower.

      BTW, Ziebart’s warranty covers only the original owner unless $25 is paid by the next owner within 30 days of purchase.Since there was no Ziebart paperwork with the car and since ther were no asterisks in Ziebart’s “Lifetime Warranty” ads, I thought nothing was needed but to show the shop the dozens of “Z’ed” hole-caps in my car’s body.

  • avatar

    I usually wash and wax right before winter, then go to a car wash when it’s spring for an under body wash. I wash and wax by hand from then on, until it’s close to winter and I repeat the cycle.

    No rust so far except the few small parking lot dings on the non-composite body parts.

  • avatar

    Lots of good advice here. One of the reason why there are still collector cars from the eras that rusted badly is because people parked the nice car during the salt season and drove a beater till the weather cleared up.

    I never understood the point of owing a high end SUV like a ‘sclade’ or a Benz, if the purpose is to drive it when the roads are dangerous? Most people won’t wear their best clothes when they have dirty work to do, but we’ll drive cars worth 40-50 grand in conditions that make damaging them more likely.

    Park your nice car and drive something you don’t care about till the roads improve.

  • avatar

    In Upstate NY the roads are covered with salt and sand. Undercarriages bear the brunt of the damage. Periodically, I flush the underside by running it through an automatic car wash. On the first warm day in early Spring, I thoroughly wash the undercarriage at home. This includes removal of all the grit from the wheel wells. This leaves small mounds of gravel and sand on the driveway. In 10 years, the only rusted spot is around one of the jacking points where the jack wore through the paint.

  • avatar

    Many thanks for all of your points and suggestions.

  • avatar

    Having worked in the car business here in the rust belt, and having seen many different approaches, my conclusions are:

    (1) Wash the car anytime it is near-melting, and again in the spring. Otherwise let it freeze.
    (2) Hit it with a wet-type (ie: Krown, Metropolitain, Rust-Check) rust spray every year or two, preferably without drilling holes.

    Do it right and your Camry will look new after 15 years. Do it wrong and it will be Swiss Cheese by your third set of tires.

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