Why won't my car start in cold weather?

Cold weakens marginal batteries and thickens engine oil, so the most common cause is a battery near end of life. Glow plugs are the diesel equivalent.

Here's a quick, honest answer from a working UK mechanic — what causes it, what it costs to fix, and what to do next.

Should I use a battery conditioner? — Yes if the car sits unused for more than 2 weeks. A trickle charger doubles battery life.

Is it worth pre-warming with a block heater? — In Scotland and northern England, yes — especially for diesels.

Bob's Mechanical Repairs — independent family-run garage in Birnam, Dunkeld, Perthshire. Call 01350 727 276 or email bob@bobsmechanicalrepairs.co.uk.