Ontario doesn't ease you into winter. One week you're driving with the windows down; three weeks later you're scraping ice at 7am in the dark and hoping your battery has enough juice to turn the engine over. If you haven't prepared your vehicle before that first freeze, you're going to find out the hard way what you forgot.
We've been servicing vehicles through Wellington County winters since 1979. Here's what we check on every vehicle before the cold season hits — and what you should be thinking about on yours.
Winter Tires: The Most Important Thing You Can Do
If you do one thing to winterize your vehicle, make it this. Winter tires are not just about traction in snow. They're about traction in cold. All-season tires harden at temperatures below 7°C, reducing grip on dry pavement, wet pavement, slush, and ice. Winter tires are made from a rubber compound that stays pliable in cold, and their tread pattern is designed to evacuate snow and channel slush.
The difference in stopping distance is significant. At -10°C, a vehicle on winter tires can stop from 50 km/h up to 40% shorter than the same vehicle on all-season tires. That's not a marginal improvement — that's the difference between stopping in time and hitting something.
Ontario doesn't mandate winter tires province-wide (Quebec does), but your auto insurer may offer a discount for using them. Check your policy. The savings can partially offset the cost of a second set of tires.
The generally accepted rule: winter tires go on when daytime temperatures drop consistently below 7°C. In the Guelph area, that typically means mid to late October. They come off in April once temperatures are reliably above 7°C during the day.
Battery: Cold Weather Reveals Weakness
Batteries lose a significant portion of their cranking power in cold weather. A battery that's at 80% capacity in summer may barely turn the engine over at -20°C. If your battery is more than three years old, have it tested before winter — not after it leaves you stranded in a parking lot in February.
Battery testing takes about five minutes and most shops do it for free or a small fee. A load test will tell you whether the battery can hold voltage under demand. If it can't, replace it before winter rather than during it when shops are busy and you're stressed.
Signs your battery is struggling: slow cranking on cold mornings, the engine hesitating before starting, or the battery warning light flickering. Don't ignore these. Cold weather will push a marginal battery over the edge.
Engine Coolant: Freeze Protection and Corrosion
Your coolant does two things: it prevents freezing in cold weather and it prevents boiling in hot weather. But it also degrades over time. Old coolant becomes acidic, corroding aluminum components, water pump internals, and radiator fins from the inside out.
Check the freeze protection level with an inexpensive coolant tester (or have your shop check it). It should protect to at least -40°C. If it's marginal, a coolant flush and refill is relatively inexpensive — typically $100–$150 — and prevents much more expensive cooling system repairs down the road.
Also check the coolant level in the overflow reservoir. Low coolant level suggests either a leak or that the system was topped up with water at some point, diluting the mix. Both need attention before winter.
Oil: Viscosity Matters More in Cold
Engine oil thickens in cold temperatures. When you start a cold engine, the oil needs to flow immediately to lubricate bearings and valve train components. Thick, degraded oil flows slowly, meaning the first few seconds of engine operation have inadequate lubrication — and that's where a lot of engine wear happens.
If you're due for an oil change, do it before winter rather than after. Full synthetic oil flows better in cold temperatures than conventional oil, which is one of the reasons most modern manufacturers specify synthetic. If you're running conventional oil in an older vehicle, consider switching — your engine will thank you every cold morning.
Check your owner's manual for the recommended viscosity for cold weather. Some manufacturers specify a different viscosity range for very cold climates. In most cases, 5W-30 or 0W-20 full synthetic is ideal for Ontario winters.
Windshield Washer Fluid: Don't Underestimate This
This sounds trivial until your washer fluid freezes in the nozzles and you're driving on a salty highway with road spray covering your windshield and no way to clean it. Use washer fluid rated to at least -40°C. Don't top up with water — you'll dilute the freeze protection and potentially freeze the lines.
Also check your wiper blades. Summer blades don't shed ice and snow well. Winter-specific blades have a rubber boot covering the arm mechanism that prevents ice buildup. If your summer blades are already more than a year old, replace them with winter blades in October and put your summer blades back on in spring.
Brakes: Cold Season Inspection
Brakes are a year-round safety item, but winter puts extra stress on them. Salt and moisture accelerate rotor corrosion. Cold temperatures affect brake fluid. And stopping distances increase on snow and ice regardless of how good your brakes are — you want to make sure they're doing their maximum job.
If you haven't had your brakes inspected in the past year, do it before winter. A technician will check pad thickness, rotor condition, caliper operation, and brake fluid. Brake fluid absorbs moisture over time, which lowers its boiling point and can cause issues in demanding conditions. Most manufacturers recommend flushing brake fluid every two to three years.
Four-Wheel Drive and AWD: Don't Assume It's Working
Four-wheel drive systems and AWD differentials need their own fluids changed on a schedule. Old differential fluid loses its viscosity and protective additives, leading to wear in the transfer case and differentials. If you can't remember the last time the differential fluids were changed, have them checked.
Also, if your vehicle has a selectable 4WD system (a lever or button you use to engage 4-high or 4-low), engage it a few times in the driveway before winter to make sure it's working. Selectable systems that haven't been used all summer sometimes have sluggish actuators. Better to find that out in your driveway than on a snowy country road.
From our service team: The most common issue we see in November is customers coming in after their car won't start, or after a close call on slippery roads. Almost every one of those situations could have been avoided with a pre-winter inspection in October. Don't wait for a problem — book it early while we have availability.
Emergency Kit: Keep One in the Vehicle
Even a well-maintained vehicle can leave you stranded — a flat tire, a slide into a ditch, a dead battery when it's -25°C. Keep a winter emergency kit in your trunk. At minimum: jumper cables or a portable jump starter, a blanket, a small shovel, sand or kitty litter for traction, a scraper and brush, a flashlight, and a basic first aid kit.
If you do a lot of rural driving or highway commuting, add an emergency flare or reflective triangles, extra warm clothes, and a phone charger cable. It's a few dollars in insurance against a very bad situation.
The Bottom Line
A pre-winter vehicle inspection takes about an hour and covers everything above. Battery, tires, brakes, fluids, wipers — a technician can check all of it in one visit. It's not expensive, and it almost always finds something you'd rather fix in October than deal with in January.
Our service team at Marden Motors does winter readiness inspections and can install winter tires if you need a set. Call ahead — October gets busy. Getting in early means you're covered before the weather turns, not scrambling for an appointment when it already has.