Drivers warned pushing popular button could cost you £100s – short journeys are the worst

DRIVERS are being warned to avoid press popular buttons to save £100s in fuel bills - and how shorter journeys are the worst.

Motorists risk "increasing" fuel consumption by pressing a button found in every car across the UK.

Tesco, Asda, Morrisons and Sainsbury's drivers can boost their petrol and diesel fuel economy rates by reducing air conditioning and heating usage, according to . 

The insurance firm says: “Both air conditioning and heating use engine power and therefore increase your vehicle's fuel consumption.

"Therefore, try to dress for the weather even when in your car.”

A study by Emissions Analytics found the impact of air-conditioning on hybrid cars was nearly double, with fuel efficiency dropping 6.1 per cent in a hybrid car on average.

This compared to just 3.8 per cent for a standard petrol car and 4.6 per cent for a diesel.

Air con can drive up fuel consumption by up to 10 per cent.

But it's a balancing act as, conversely, opening the windows at higher speeds can increase it by as much as 20 per cent.

Closing your windows if driving over 40mph can prevent drag on the vehicle and creating stronger wind resistance.

Kwik Fit added: "The compressor requires energy to run your vehicle’s air conditioning system and so will use a small amount of fuel whenever the system is running.

"It could increase your fuel usage by as much as 10 per cent, and the effects are particularly noticeable on short journeys.

"When you initially set off, the air con has to work hard to bring the internal temperature down to a comfortable level.

"However, once the car has cooled enough, you can choose to reduce the flow rate, increase the temperature or turn the air con off altogether."