With temperatures rising and fuel prices still high, many will be looking to keep cool and boost their fuel economy this summer. On average, drivers are seeing petrol prices of 178.93p per litre, while diesel owners face higher costs at 189.30p every time they fill up.
While the RAC says prices should fall, many will still be looking at ways they can save and make their fuel last longer.
When driving in warm weather, motorists will usually opt for having the windows open or by using air conditioning.
While many may overlook their impact on their fuel efficiency, both options have a huge impact on how the fuel is used.
Air conditioning is very energy intensive, while open windows can reduce the drag of the car, making the car work harder and burn through the fuel quicker.
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He said: As such, the 45mph figure is a guide, but a fairly good one.
“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 percent but opening the windows at higher speeds can increase fuel consumption by as much as 20 percent.”
A number of other studies have also followed, one of which found that hybrid car fuel economy is harder hit by air con use than conventional combustion-only cars.
More research, from Emissions Analytics, found that the impact of air conditioning on hybrid fuel economy was almost twice as much.
Fuel efficiency dropped 6.1 percent in a hybrid car on average, compared to just 3.8 percent for standard petrol car and 4.6 percent for a diesel.
Mr Evans continued saying: “While the 45mph line is a good guide, things get a bit more complicated when you are in bumper-to-bumper traffic.
“In these situations, it is probably best to avoid using air con or opening your windows.
“However we know that in hot conditions that might be uncomfortable, so as a solution you could turn on the air con but close your air vents.
“The air con merely recycles the cabin air rather than drawing the air from outside, where there is nose-to-tail line of traffic all belching out exhaust fumes.”
Other options for keeping the car cooler and not relying on air conditioning include parking in the shade or in a garage.
Tinted windows could also provide benefits for drivers, as will heat deflectors.
A car window tint can effectively reduce the heat given off by direct sunlight by as much as 70 percent inside a car.
Since the car will be cooler, drivers may be less likely to use the AC.