January is the month when many drivers notice their fuel gauge dropping faster than usual. You're not driving any differently, yet somehow you're filling up more often. The culprit? Cold weather.
According to official fuel economy tests, your car's efficiency drops by around 10% at -5°C compared to 20°C. For short trips under four miles, that penalty can reach 20% or more. With petrol currently averaging 135p per litre and diesel at 143p, that's money draining from your wallet every time you turn the key.
Why Cold Weather Kills Fuel Economy
Your car wasn't designed to run efficiently in the cold. Several factors combine to make winter driving more expensive:
1. Your Engine Takes Longer to Warm Up
Modern engines are most efficient at their normal operating temperature, typically around 90°C. In cold weather, it takes significantly longer to reach this sweet spot.
Until the engine warms up, your car runs on a fuel-rich mixture – using more petrol or diesel per mile to compensate for the cold. The bigger the gap between outside temperature and optimal engine temperature, the longer this inefficient phase lasts.
2. Thicker Oil Creates More Resistance
Engine oil thickens in cold conditions, creating more internal friction. Your engine has to work harder just to turn over, burning extra fuel in the process. This effect is most pronounced in the first few minutes of driving.
3. Your Tyres Lose Pressure
For every 10°C drop in temperature, your tyre pressure falls by about 1-2 PSI. Underinflated tyres increase rolling resistance, and the result is up to 5% worse fuel economy – not to mention reduced grip on icy roads.
4. Denser Air Increases Drag
Cold air is denser than warm air, which means your car faces more aerodynamic resistance at speed. This particularly affects motorway driving, where the extra drag adds up over distance.
5. Heated Seats, Demisters and Lights
All those winter comforts – heated seats, rear window demisters, headlights on all day – draw power from your alternator, which in turn puts extra load on the engine. Air conditioning used to demist windows is particularly power-hungry.
6. Diesel's Winter Problem
Diesel drivers face an additional challenge. While petrol freezes at around -60°C (virtually impossible in the UK), diesel can start to gel in very cold weather. Refineries switch to "winter diesel" formulations with additives to prevent this, but these blends can be 2-3 mpg less efficient than summer diesel.
The True Cost of Cold Weather Driving
Let's put some numbers on this. A driver covering 8,000 miles per year in a car averaging 45mpg in summer might see that drop to 40mpg in winter months.
At current prices, that's roughly:
- £15-20 extra per month for petrol drivers
- £18-25 extra per month for diesel drivers
Over the winter months from November to March, that adds up to £75-125 in additional fuel costs that many drivers don't budget for.
How to Fight Back: Winter Fuel-Saving Tips
Don't Idle to Warm Up
It's tempting to let your car idle for five minutes on a frosty morning, but this is one of the worst things you can do for fuel economy. Modern engines warm up faster when driven gently. Most manufacturers recommend driving off after 30 seconds – just take it easy for the first mile or two.
Check Your Tyre Pressure Monthly
This is the easiest winter fuel saving you can make. Check pressures when tyres are cold (before driving) and inflate to the manufacturer's recommended level – usually found on a sticker inside the driver's door frame or in your handbook.
Combine Short Trips
Short journeys are fuel economy killers in winter because your engine never reaches optimal temperature. Where possible, combine errands into one longer trip rather than several short ones. Your engine stays warm between stops, maintaining better efficiency.
Park in a Garage or Sheltered Spot
A garage doesn't just protect your car from frost – it means your engine starts from a warmer baseline, reducing that inefficient warm-up period. Even parking against a building or hedge can help.
Remove Unnecessary Weight
Every 50kg of extra weight costs you around 2% in fuel economy. Clear out the boot of items you don't need. Those bags of rock salt, emergency supplies you never use, or forgotten sports equipment all add up.
Plan Your Route to Avoid Congestion
Stop-start driving in traffic is always inefficient, but it's worse in cold weather when your engine keeps cooling down between accelerations. If possible, time your journeys to avoid rush hour, or take a slightly longer route that keeps you moving.
The Silver Lining
The good news? Fuel prices have actually fallen slightly since the December peak. Petrol dropped 1.8p per litre last month, while diesel fell 2.3p. Combined with the fuel duty freeze continuing until September 2026, now is actually a reasonable time to be filling up – even if you're doing it more often than you'd like.
Understanding why your car uses more fuel in winter is the first step to minimising the damage. A few simple habits can easily save you £50 or more over the cold months – money better spent elsewhere.