As the temperatures heat up outside, the first you think probably think of when getting into your car is turning the air conditioner on. Why wouldn’t you? If it’s 80 degrees Fahrenheit outside, then it has to be at least 110 degrees inside that rolling greenhouse, right? Believe it or not, it may actually be a poor decision to turn on the A/C this summer, here are a few reasons why.

1. Turning on your car’s air conditioner on a hot day can be harmful to your health

When it’s sweltering inside your car, the first thing you probably do is turn the A/C to full blast. But according to SILive, that immediate cold blast of air can actually be harmful to you: “Your car may actually be killing you by releasing toxic levels of a cancer-causing chemical called benzene. Dangerous levels of this chemical are released from plastic surfaces of automobile interiors.”

What should you do instead? You can roll down the windows and turn on the A/C when you get going. That way, the chemicals are at least exiting the cabin while the car’s interior cools down.

2. Your car’s gas mileage will suffer

It’s no secret that your car will get worse fuel economy when you drive with the A/C on. According to the EPA, using the air conditioner in your car can lead to a reduction in fuel economy by up to 25%. Reader’s Digest also confirms this fact, reporting that the Society of Automotive Engineers (SAE) compared driving with the A/C on versus the windows down.

They tested cars that drove 31 mph, 50 mph, and 68 mph in 86-degree weather and found that driving with the windows down is more efficient than using the A/C. Of course, driving with the windows up and the A/C off yielded the best results, but that could be too uncomfortable on a hot day.

3. The air conditioner robs the car’s engine of horsepower

Since your car’s air conditioning system runs off the engine, the engine loses power whenever the A/C is turned on due to the drag put on it. As far as how much power your car’s engine loses can depend on the size of the engine and its power output. But generally speaking, you can expect a decrease of around 10 hp and 10lb-ft of torque when that little A/C button is activated.

Don’t turn on the A/C when driving

Considering your car can lose power, get worse fuel economy, and even be harmful to your health when you blast the A/C this summer, it might be a good idea not to. If you would rather get the most out of your car altogether, you can always use the tried-and-true method of rolling all of the windows down and driving.

Back in the day, people used to call it “two-sixty air conditioning,” which meant that you roll two windows down and then drive 60 mph on the freeway to cool down the car. But if you still can’t take the heat, then, by all means, turn on the car’s A/C. Just remember that it comes with a few consequences.