/ Motoring

Car defrosting – expensive and potentially dangerous

A very frozen car

Direct Line Car Insurance has claimed UK motorists waste nearly £50m of fuel each winter by leaving their cars to idle and warm up while they defrost the windows. But it’s a hazard, too.

Nobody likes cold morning starts. The tempting option of starting the car, setting the blowers to max and leaving it to idle until the windows are clear sounds far less pain-inducing than hacking at ice-covered windows with a scraper.

But according to some rather extensive calculations by Direct Line, those who are opting to leave their cars idling are wasting extortionate amounts of money and fuel.

According to the insurer, the fuel wasted on defrosting cars in the four months from November to February equates to over 300 million road miles. That’s enough for someone to drive an average-sized car around the world more than 13,000 times.

And it appears lots of us are doing it. A survey carried out by the insurance group found four in 10 respondents said they leave their cars to idle, unattended.

Letting your car idle to defrost is risky, just ask Paul Scholes

Manchester United and former England international footballer Paul Scholes knows this all too well, after his car was stolen from his driveway in January.

A new group of offenders being referred to by police as ‘ice bandits’ are claimed to be targeting vehicles left unattended to defrost, and Paul Scholes appears to fallen foul of them.

And while the theft of a Chevrolet Captiva (possibly a freebie for Manchester United players from the club’s sponsors, Chevrolet) might not have much of a financial impact on a multi-thousand-pound-a-week professional footballer, it may be more of an issue for consumers. Especially if your car insurance cover could also be invalidated due to negligence.

Letting your car idle to defrost is dangerous, just ask my mum

A couple of winters ago, my family also felt the repercussions of letting a car idle to defrost.

One frozen January morning, my dear mother had forgotten she’d left the car in first gear with the handbrake off the night before. When she leaned into it and started it the following morning, it leapt through the front wall of the house. I will never forget eavesdropping on my dad’s phone conversation to the insurance company to explain how she’d crashed her car into the bathroom.

So how do you go about defrosting your car? Are you an early morning ice-scraper wielder, a seasoned aerosol de-icer or a frowned-upon idler?

Em says:
3 March 2013

All waste is relative and I can’t see how it is as “extortionate” as some car insurance premiums.

Anyway, what are the alternatives? Use a de-icer costing around £5 per litre, which is also made from petroleum products? I typically get through 2-3 spray bottles in a winter season. But in money terms that’s equivalent to about 7-10 litres worth of fuel, which would provide about 5 minutes of idling time per icy day throughout the winter season. And that doesn’t take any account of the fuel saving by driving off on a slightly warmer engine.

Scraping is not always effective – certainly not on frozen rain. Driving away immediately after using de-icer or elbow grease with a stone cold engine is just asking for trouble. The windows fog up in no time, particularly when de-icer is used, which has the effect of cooling the glass even further. (You didn’t think it melted the ice by warming the windscreen, did you?)

In my view, that is far more of a safety hazard than leaving a car idling (with the handbrake on) in the driveway. But then I certainly wouldn’t leave my car in a vulnerable place without being in the driver’s seat.

Another nonsensical survey supported by some sensational, but meaningless, statistics I’m afraid. Maybe the entire car journey is rather pointless; after all, most people end up back where they started from. How about this for a real money-saving idea – stay at home!


Start the engine by all means but stay with the car and scrape the windows or brush off the snow. It should not take long, but if you really must leave it on your drive with the engine running, the driver’s door can probably be locked with the spare key. On my car, the lock is hidden by a removable cover.

The Highway Code says not to leave a car unattended if it is on a public road, and anyone daft enough to do this may face a penalty – theft of their car and void their insurance for theft. 🙁

I assume that everyone knows that air conditioning is great for preventing the windows misting up when setting off in cold conditions. Another benefit is that running the air conditioning periodically over winter can help keep it working properly.

Em says:
3 March 2013

A good point about air conditioning wavechange, although it is of most of benefit on damp days, rather than when freezing conditions have taken all the humidity out of the air and deposited it on the windscreen!

And good to bring it to the attention of the unaware, but then I suspect there is another “shock horror” survey somewhere about how much fuel is wasted by motorists leaving their a/c on over the winter.


I don’t leave my car unattended to defrost.

My method for the past 30 years, is quite simple…

Start the engine, put the blower on the windscreen, heated rear window on, and pour a jug of luke warm water over all the windows.

Ok, some of you will be saying, bad idea, it will crack the glass, but it doesn’t, really.
If you were to pour boling water on it out of a kettle, then obviously you’re asking for trouble, but luke warm out of the tap is absolutely fine.

it’s the quickest way to do do it, and I’m on the road in a couple of minutes 🙂

Em says:
4 March 2013

I agree the jug of warm water method works most of the time, although if you have any slight fault (chip, crack) it may well fail at that moment – I know this from experience. My preferred method is to park the car in the garage or use a hair dryer to warm the glass.

However, neither of these methods are practical if you are away from home or returning from work and your car is frozen solid.

Hence the advice not to idle your engine says what … ???


I find a scraper and de-icer works fine, though both have to be good quality. The only time I had to use warm water was when all the car doors were frozen shut. 🙁

par ailleurs says:
4 March 2013

The advice has long been to stay with your car while defrosting it. If you have to park it on the street then you’ve no choice. Hypothermia anyone? Obviously the best bet is to garage it at home but where to store that mountain of rubbish that lives in most garages? And that doesn’t help when you’ve left it parked all day at work.
De-icer sprays are good but only work on the outside and invariably any condensation inside will freeze with or without air-con. Scraping helps but only with a really good quality rubber blade and any odd bit of grit will scratch a screen. Starting the engine and letting it do the job is slow but effective and meanwhile you’ve put an inordinate amount of strain on the cold oil and accelerated your engine wear.
There seem to be two answers here. Firstly give up work and don’t leave the house first thing in the morning. Secondly, consider emigrating to warmer climes. OK I’m being my normal droll self here but my advice is ultimately no less helpful than that from Direct Line. People live in the real world of work and have to do things that they’d rather not, like de-ice the car at some ungodly hour. There’s no single, easy answer and Direct Line is not helping either.


I would start the car, switch on the heated rear window, the air blower on the front window, then get out of the car, lock it with the spare key, then go back inside. 5-10 mins later and nicely defrosted and still locked car.

derek black says:
4 March 2013

Agree that it has to be high quality de-icer. Got some from supermarket and it was rubbish – took a whole can to defrost the windscreen alone. Have Which? any best buys to tell us about?


I would be surprised if any modern de-icers are as effective as products that were around 30 years ago. The old versions contained quite a lot of methanol, which is a better de-icer than ethanol, propane-2-op, and ethanediol – some of the active components of modern de-icers. Methanol is quite toxic and since people sometimes use de-icer on the inside of their windscreen, I can see why modern products contain little or no methanol.

Windscreen washer fluids are another problem. They often freeze up, but at least there are some good quality products available – at a price.

Miika I. says:
4 March 2013

Turn on the engine, switch the heated rear window on and the air blower on the front window (unless you have a heated front window aswell). Then take your scraper-brush combo and first get the snow off. Then start scraping from the side which are usually easier. When you get to rear window (after the first side) it’s melted and easy to clean. Proceed to the other side and the increased heat inside has made the side windows easier to scrape too. Front window is the last and by now it’s almost melted and very easy to scrape.
Whole thing is 3-5 mins depending on the thickness of the ice.

Miika I.

the dragon. says:
7 March 2013

I’ve probably missed something that has already been said, but covering the screen on frosty nights is a good start! Of course all the glass must be clear before you drive. Secondly, it used to be and I expect it still is an offence to leave a car unattended on a public highway without first setting the handbrake and turning off the engine. OK on your own property, not on the road, not advisable anywhere.

Chriscardiff says:
8 March 2013

I have one of those silver thermal padded screens meant for leaving inside the windscreen on a hot sunny day. It works a treat on the outside for keeping frost off in winter, held in place by the wipers.