Exact speed where using A/C becomes much cheaper than opening car windows revealed
As the mercury rises, drivers up and down the country are facing the same daily dilemma: crank the air con and watch the gas gauge drop, or roll the windows down and just deal with the noise.
It turns out there's a best answer, but it depends entirely on how fast you're actually driving.
Tom Preston, managing director of Hippo Leasing, has weighed in on the debate that seems to resurface every time there's a heatwave, and his advice might change how you approach your next long drive.
Per The SUN, Preston said the instinct to fling the windows open the second you get in a baking hot car is understandable, but it's not smart.
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"Instead, open the windows for a minute before setting off to let the trapped hot air escape," he said, before pointing the air vents towards the footwells so the cooler air pushes the warm air up and out of the car.
Once the cabin has actually cooled down, that's when you need to make a switch.
Preston says drivers should close the windows and switch to air recirculation mode, which helps the system cool the car far more efficiently than fresh air ever could.
What speed does opening a window use more gas than the AC?
While driving with the windows down feels like the free option, Preston says that once you go above 45mph, the extra aerodynamic drag created by open windows can actually burn more gas than simply running the air conditioning.
In other words, that satisfying blast of air through an open window on the freeway could be costing you more at the pump than just keeping the windows shut and letting the AC do its job.
It's a detail that flips a lot of people's assumptions about 'free' cooling, and one that's worth remembering next time you're debating whether to reach for the window switch or the AC dial on a long drive.
How to cool down a hot car quickly without wasting gas
Preston also flagged a few extra tips that, while not directly about saving cash, are worth knowing if you want to keep your car running properly through the summer.
Recirculation mode shouldn't be left on for more than around 30 minutes at a time, as carbon dioxide can build up inside the cabin and potentially leave the driver feeling drowsy behind the wheel.
It's also worth avoiding recirculation in wet weather, since it can cause the windows to fog up more quickly, though it comes in handy during heavy traffic by helping to keep exhaust fumes out of the cabin.
In extreme heat, Preston suggests switching off Eco and stop-start modes altogether, as both can reduce how effectively the air conditioning actually performs.
And it's not just a summer issue either. Running the air con occasionally during winter can help stop mould and bacteria building up inside the system, while getting it re-gassed every couple of years keeps its cooling performance up to scratch.
Thomas Bamford