Why won’t my car start in cold weather? Top tips to get your motor back on the road

FROSTED windows, icy roads, non-starting engines and being snowed under are just a few of the problems we need to be prepared for this winter.

We can’t help with all of it, but we can explain what you can do if your vehicle isn’t starting with our guide to getting you back in gear.

 Cars - like most humans - don't react well to the cold weather


Cars – like most humans – don’t react well to the cold weather

Why won’t my car start?

Not unlike humans needing layers of clothes to brave low temperatures, cars also need a little preparation to get going.

When cars won’t start, it’s often because their engine oil has thickened in the cold, which increases friction and makes it harder for the starter motor to spin the engine.

Cold, damp weather can sometimes play havoc on batteries as vehicle electrical systems have to work a lot harder.

The RAC says the majority of their winter call-outs are to do with car batteries.

Should I leave my car running to warm it up?

Avoid doing this if you can. Leaving your car engine going before you start driving doesn’t actually help the engine, but just ramps up your fuel use and emissions.

Cars older than 20 years do need warming up to get going in the cold weather.

But most modern engines adjust their temperature accordingly, so car experts say you shouldn’t leave your car running for more than 30 seconds before driving.

But what about defrosting my car?

Pouring hot water on a frosted windscreen may seem like a good idea, but it can actually lead to the glass shattering if there’s any kind of small crack in your screen.

The best method, according to meteorologist Ken Weathers, is to create your own solution using rubbing alcohol and water from a spray bottle.

Mr Weathers says he mixes 1/3 of a cup of water with 2/3 of a cup rubbing alcohol to produce the defrosting spray. It works because rubbing alcohol has a freezing point of -128°C.

Always keep a car window ice scraper in the car as a back up, too.

How to solve a car battery problem

To try and prevent a battery problem from happening in the first place, it can help to charge your battery at least once a week during the winter months, particularly if it is more than three years old.

A car battery comfort indicator can help monitor its condition. But if your battery isn’t charging well at all, it might be worth getting it replaced when you can.

You can also do a few small things to help keep your battery in a decent condition:

  1. Switch off all loads including lights, wipers, heater etc before switching off your engine at the end of your journey (and make sure they’re off before you turn the ignition on.) This helps prevent an unnecessary drain on your battery.
  2. Avoid using heaters, heated screens and heated seats for longer than you have to
  3. Park your car in a garage if you’re able to, especially in very cold temperatures
  4. Get your battery properly tested, especially if your car’s over four years old


Using the right oil

Check your car’s manual to find out which oil to use in cold conditions.

Modern synthetic oils flow quite well in the cold, as long as you use the right one.

You’ll need to use a multi-weight oil, designated by two numbers (such as 10W-40, which is common).

The first number, with the W, is for winter; lower means it flows more easily.

5W- and even 0W- oils exist, but check your manual. It’s even more important if your car uses conventional, rather than synthetic, oil.

Last resort

And if your car won’t start at all, you may need to use your jump leads – here’s a guide to how to do it.

For more tips from car experts RAC on navigating your car in any weather, click here.

Finally, read our guide on how to drive in snow and ice here.


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