The Cheap Car Accessory That Can Improve Fuel Economy In Hot Weather

If you live in a part of the country where sweltering temperatures are common, you'll be all too familiar with the inconvenience of opening your car doors on a hot day and getting hit with a wave of heat. Modern cars are well insulated, and if they're left in the sun for any length of time, they act like greenhouses and can quickly reach temperatures that make them uncomfortable to sit in. Pushing the snowflake button and turning the A/C up to maximum can help cool the cabin back down to a more pleasant temperature, but it can also have a significant effect on your car's fuel economy.

According to the Department of Energy, leaving the A/C on full blast in very hot conditions can reduce your vehicle's fuel economy by 25% or more. The negative effect is more pronounced on shorter trips, when you'll spend less time in your nicely cooled car once the A/C has done its job.

The easiest way to make sure your car's fuel economy isn't impacted is to try and reduce the warming effect on the cabin while it's parked. Parking under a shaded area is one way of keeping it cooler for longer, but if that isn't an option, then a sunshade is a good alternative. This cheap accessory can make more of a difference than you might think, since reducing the temperature of the cabin by even a few degrees means the A/C has less work to do when you return to the car and drive off.

Sunshades are cheap and can help improve your car's fuel economy by ensuring the cabin stays cooler, but they're not the only way that you can reduce your A/C usage. If your car's cabin is significantly hotter than the air outside, rolling the windows down for a short period can also be more fuel-efficient than using the A/C. It's better to roll the windows down when you're traveling at slower speeds, since open windows can have a more significant negative impact on a car's aerodynamic efficiency at higher speeds.

Driving with the windows down on the highway almost inevitably means you'll use more gas, but exactly how much more you'll use will depend on the make and model of your car. A 2014 study by Oak Ridge National Laboratory found that a Ford Explorer only saw a drop in efficiency of between 1% and 4% when all four windows were opened, but a Toyota Corolla recorded a much higher drop in efficiency, losing 4% to 8.5%.

If your drive includes a stretch of lower-speed roads before you hit the highway, the most efficient way to cool the cabin would be to roll the windows down at first, then roll them back up and turn on the A/C when you reach the highway. It's also a good idea to open your car's sunroof when you're initially trying to cool the cabin down, if your car has one. Compared to opening the windows, a sunroof usually has a much smaller negative impact on aerodynamics, and so it shouldn't dent your car's fuel efficiency.

It's also worth making sure you aren't unknowingly wasting your car's fuel in other ways if you're trying to keep gas bills to a minimum. Among other things, you'll want to make sure that you remove roof racks when they're not in use, minimize the number of unnecessary items you carry around, and make sure your tires are inflated to the correct pressure.