What cold weather actually breaks
Cold does not create faults so much as reveal them. A battery at 70 per cent capacity works fine in September and fails in January, because cold thickens the oil the starter has to turn and simultaneously reduces the battery's available current. Both curves move the wrong way at once.
Tyres lose roughly 1 to 2 PSI for every 10°C drop. Rubber compounds harden below about 7°C, which is why grip falls away before ice is anywhere in the picture.
Battery and charging
The single highest-value winter check. A load test takes minutes and tells you whether the battery will survive a cold snap. Anything over four years old on a car doing short journeys should be tested rather than trusted, and the charging system should be tested alongside it, since an undercharging alternator produces identical symptoms.
See the full battery warning signs guide for what to look for.
Tyres and tread
- Legal minimum is 1.6mm across the central three-quarters. Wet grip degrades noticeably below 3mm.
- Check pressures cold, monthly through winter, against the placard in the door shut or fuel flap.
- Look for uneven wear, which points at alignment or suspension rather than tyres.
- Winter or all-season tyres are worth considering if you regularly drive in rural or upland areas.
Coolant and antifreeze
Antifreeze is not just about freezing. It carries corrosion inhibitors that protect the water pump, radiator and head gasket surfaces, and those inhibitors deplete over time. Weak coolant in a cold snap can freeze in the radiator and crack it, and depleted coolant corrodes quietly all year.
Concentration is checked with a refractometer in seconds. It is part of every service we carry out, and worth asking about specifically before winter.
Visibility
- Wiper blades: replace if they smear, chatter or leave lines. They are consumables, not fittings.
- Screenwash: use a proper winter concentration, not water. Frozen washer fluid at 70mph on a salted motorway is genuinely dangerous.
- Lights: check every bulb including brake and reverse, and clean the lenses. Road salt film cuts output significantly.
- Demister and pollen filter: a loaded cabin filter is the usual cause of a screen that will not clear.
The kit worth carrying
Not the exhaustive list, the one people actually use: a phone power bank, a torch, a warm layer and a blanket, de-icer and a scraper, a small shovel if you are rural, and jump leads or a lithium jump pack. A jump pack is the single most useful item on this list, and it lives in the boot for years without complaint.