Getting your car ready for winter: the order to do things in
Most people do the right things, just in the wrong order. And in the wrong order, some of those things work against you.
The short rule: clean, inspect, repair, protect. In that order, and all of it before the end of October. Rustproofing sprayed on a dirty underbody seals the dirt and moisture against the metal for six months.
Why October, not November
Two dates frame everything else.
The first is salting. Quebec spreads about 1.5 million tonnes of road salt a year on its road network. The first preventive salting doesn't happen when it snows. It happens when the pavement might freeze. On the North Shore, that means late October or early November, often on dry asphalt under a blue sky.
The second is the rustproofing window. CAA-Québec puts the ideal time between August and October, precisely so the product is in place before the salt arrives.
The two dates touch. If you book your rustproofing for November 15, your underbody has already taken two weeks of salt, and nobody washes it before spraying oil over it.
What salt really does
There's a stubborn misconception: salt doesn't eat paint. Paint in good condition stands up to sodium chloride very well.
The real mechanism is sneakier. Salt dissolved in meltwater forms a solution that conducts electricity. Wherever the metal is bare (a stone chip, a parking-lot scratch, a poorly covered weld), that solution closes a circuit between two points on the steel and corrosion starts. It keeps going as long as there's moisture. And brine doesn't freeze at zero: it stays liquid well below, which means the reaction continues for weeks in a corner that never dries.
Hence three practical consequences:
A 2 mm chip matters. It's the way in. Without one, salt only makes things dirty.
Spots that never dry count double. Wheel wells, door bottoms, tailgate edges, around the muffler.
Contact time matters more than quantity. A car washed every two weeks and a car washed once in March get the same salt. The second one keeps it for 120 days.
The six steps, in order
1. A full wash, underbody included. Late September, early October. This isn't a cosmetic wash: it removes the summer's road dust, tar, sap and bugs before anything goes on top. The underside matters as much as the top, because that's where the rustproofing goes.
2. Inspect outside, in daylight. Not in a garage under a yellow bulb. Crouch down and look: the bottom of the doors, the rear lip of the wheel wells, the front bumper, around the windshield, and the door sills with the door open. You're looking for three things: chips down to the metal, bubbles under the paint, orange marks.
A bubble is rust already working underneath. A touch-up pen won't fix it.
3. Touch up the chips. Your car's exact paint code is on a plate in the driver's door frame, or under the hood. A touch-up pen costs about fifteen dollars. Clean the chip, let it dry completely, apply a small drop without spreading it. The goal isn't for it to look good; it's for the metal to be covered. Ten minutes here are worth more than any product in step 4.
4. Protect the paint. A wax or sealant puts a sacrificial layer between the brine and the clear coat. It doesn't make the paint invulnerable; it makes dirt stick less and come off more easily at the next wash, which means less rubbing all winter. A classic wax lasts a few months; a synthetic sealant or ceramic coating lasts longer and costs more.
5. Rustproofing, last, on a clean and dry car. The options, with the price ranges published by CAA-Québec:
Liquid oil: yearly, $100 to $175. Gets into closed cavities. Can drip in the driveway for a few days.
Semi-solid oil: $150 to $300. A compromise between penetration and staying power.
Grease: $350 to $750. Thick, and can plug drain holes: have it done by someone who knows where they are.
Permanent treatment: one time, $400 to $700. No yearly touch-up.
Electronic module: one time, $300 to $1,000 and up. Its effectiveness isn't shown by the available data.
The best time in a car's life to start is its first year. A treatment applied over existing corrosion slows it down; it doesn't erase it.
6. The interior, before the first snow. Rubber mats with raised edges, installed in October. It's the best forty dollars of the winter: calcium that stains a fabric mat works into the fibres, while on rubber it rinses off with lukewarm water. And while you're at it, take out the summer mats and look at the floor underneath: that's where moisture builds up all winter.
The four mistakes that keep coming back
Rustproofing before washing. The most common order, and the worst. The product traps wet dirt against the metal.
Waiting for the first storm. By then, every garage is booked and the salt has already been spread three times.
Counting on a heated garage. It does the opposite of what people think, and it deserves its own article. In short: the car comes in full of brine, the warmth keeps it liquid and active all night, and condensation keeps everything damp. CAA-Québec says it plainly: rapid temperature changes speed up corrosion.
Ignoring chips because they're small. A 2 mm stone chip at the bottom of a door is exactly where salt spray hits hardest. Two winters later, it's a bubble. Three, it's a hole.
The takeaway
The order: wash, inspect, touch up, wax, rustproof, rubber mats. Never the other way around.
The deadline: end of October. Preventive salting doesn't wait for snow.
The move that pays most: ten minutes with a touch-up pen. It's free or close to it, and it decides whether the rest does any good.
Sources (in French): Quebec Ministry of Transportation: environmental management of road salt · CAA-Québec: rustproofing, when, which and why