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Why winter reduces fuel economy

As if driving in the dark, rain and snow doesn’t make winter motoring hard enough, you may also notice a significant drop in your fuel economy. In cold conditions, you can see a difference of as much as 20 per cent in fuel consumption between warm summer days and cold winter ones.
So why is this? Unfortunately, you can’t change the law of physics as substances become denser as they get colder, and this affects your fuel economy in several ways:

  • Cold air is harder to drive through – for every 3 degree C drop in temperature, thicker air density increases drag by one per cent
  • Cold tyres are less flexible – the ‘rolling resistance’ on colder days is up to 20 per cent more than on a warm day because it takes more energy for the cold tyre to change shape as you move
  • Cold fluids do not flow as easily – everything from your fuel to oil and bearing grease becomes thicker and takes more energy to move
  • Cold tyres lose pressure – every 6 degree C drop in temperature will cause a drop in tyre pressure of 1psi, decreasing your fuel economy by 0.4 per cent