Drivers must 'never' touch button on dashboard unless driving over 45mph
Drivers have been told NOT to switch on the air conditioning at under 45mph - and instead wind down their windows. Motorists and road users must never use air con under 45mph because it is better for fuel consumption to wind the windows down instead, experts say.
Chris Evans from comparison site Leasing.com warned people need to keep their windows DOWN and not use air con when driving under 45mph. He said: "While all this might seem like a minor issue, getting it wrong can have a notable impact on your fuel economy.
"Using AC can increase your fuel consumption by as much as 10 per cent but opening the windows at higher speeds can increase fuel consumption by as much as 20 per cent." The RAC explained: "Don’t use your air conditioning unless you really have to as it uses engine power and therefore increases fuel consumption.
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"This goes for heat as well as cooling, so try to dress for the weather, even inside your car, if fuel efficiency is a big concern." In 2004, General Motors undertook studies to settle the issue once and for all and found a clear trend for lower fuel consumption in vehicles using the windows down, air-con off approach.
Nextbase specialist Bryn Brooker said: "If you can stand the noise, opening your windows will be a more efficient choice than running the A/C at lower speeds. Above about 50mph the drag from the open windows means the A/C is more efficient, but until you're at that speed your windows can do a lot."
The RAC added: "An age-old debate. The reality is, neither helps your fuel efficiency. Open windows increase drag, slowing the car down and increasing the amount of fuel it needs to run. Having the air-con on, meanwhile, puts an extra load on the engine, again requiring more fuel."