Winter Car PrepHow to Wash Road Salt Off Your Car in Winter
The underbody wash routine that stops rust before it starts.
Road salt is the price of winter driving in Canada: it keeps the roads passable and quietly eats your car from the bottom up. Salt mixed with melting snow forms an electrolyte that speeds up rust wherever paint or factory coating is chipped. The fix isn't complicated — it's just washing, done the right way, often enough.
How often: every two to three weeks
In salt season — roughly November through March in most of Canada — wash the car every two to three weeks, and after every major storm. The damage comes from salt sitting on metal for weeks, not from a single salty drive. A car washed regularly through winter will look the same in spring as it did in fall. A car that goes all winter without a wash will show it in the wheel wells and rocker panels by April.
The underbody is the whole point
The paint on your doors and hood can handle salt. The underbody, wheel wells, brake lines and fuel lines can't — that's where rust starts, and it's where you can't see it. Use a wash with an underbody spray option (most touchless and tunnel washes offer it). If you're washing at home, a garden hose with a spray nozzle aimed up into the wheel wells and under the rocker panels does real work. Pay attention to the inside lip of the wheel arches and the seams where panels meet — salt collects there and sits.
Touchless vs hand wash in winter
Touchless automatic washes are the practical winter choice: no brushes dragging grit across your paint, and the underbody spray is built in. Hand washing gives you more control, but doing it properly in January means cold hands and a wet driveway. If you hand wash, use the two-bucket method (one for soapy water, one for rinsing the mitt) so you're not grinding salt and grit into the paint. Either way, skip the brush-style automatic wash in winter — the brushes hold the previous car's grit.
Don't wash in extreme cold
Washing when it's below about -10°C causes its own problems: water freezes in door locks, seals and handles, and you can end up with doors that won't open — or won't close properly. Pick a day above -5°C if you can. After washing, dry the door seals and spray them with silicone lubricant so they don't freeze shut overnight. If your locks do freeze, a shot of lock de-icer (or hand sanitizer in a pinch) thaws them.
Protect before the season
The best salt defence happens in October, before the first salting. A coat of wax or paint sealant gives salt less to grab onto, and an oil-based undercoating ($150–$200 at a shop) protects the parts you can't see. Think of it as a raincoat for the underbody — it creeps into seams and stays flexible all winter. Combined with regular washing, it's the full routine.
Spring: the deep clean
When the salt season ends, do one thorough wash — underbody, wheel wells, engine bay edges — and inspect everything. Check rocker panels, wheel arches, and the fuel and brake lines for bubbling paint or surface rust. Catching a bubble in April is a $50 touch-up. Catching it next October is a panel replacement.