Until that future day when we’re all driving electric cars, most drivers need to purchase gasoline on a somewhat regular basis. So any little trick to improve gas mileage and get the most out of a tankful is welcome. But can you save on gas by sweating it out in the heat of summer and not using your car’s air conditioning system?

It’s possible. But the more you dig into this, the more you realize you won’t save enough to make much difference.

Does Your Car’s A/C Use Gas?

In short, yes, but not really enough to matter, according David Bennett, manager of repair systems for the American Automobile Association (AAA). “The AC system, when operating, does add a slight load to the engine, which could slightly increase gas usage,” he says. “This usage would not be recognized by most consumers.”

How Much Gas Does a Car’s A/C Use?

Running your car’s air conditioning does increase fuel consumption, but the specific amount can vary widely depending on several factors. The effect on gas mileage can be as little as 3% to as much as 10% or more in severe conditions.

These factors include:

1. Outside temperature: Using the AC is more fuel-efficient than driving with the windows down at high speeds, but less efficient at lower speeds.
2. Condition of the AC system: A well-maintained AC system is more efficient and will use less fuel than one that’s not in top shape.
3. Driving habits: If you tend to do a lot of stop-and-go city driving, the AC can use more fuel. In contrast, if you do a lot of highway driving, the effect on fuel consumption can be less.
4. The car itself: Smaller cars may see a larger drop in fuel efficiency when using the AC compared to larger cars.

In all, while using the AC in your car does increase fuel consumption, for most people the comfort it provides outweighs the small amount of additional gas used. You can mitigate this by using the AC as efficiently as possible, like pre-cooling your car while it’s still plugged in (for electric or hybrid cars), or parking in the shade to keep your car cooler.

Can You Save Gas By Driving Without A/C?

As much as we’d like to deliver a definite “yes!” or even a “no!” to this question, it’s more complicated than that. That’s because you need to consider your vehicle’s specific configuration and the type of AC compressor it uses.

“At a very high level, there may be a slight gas savings with the AC off and windows up,” Bennett says. “However, the savings would be minor and not realized by most consumers.”

Does Windows Down Burn More Gas Than A/C?

Turning your car into a sauna is never a smart idea. A miserable driver is a distracted, unsafe driver. But rolling down the windows and driving with them open reduces fuel efficiency even more than blasting the AC.

“Running the air conditioner when driving is actually more efficient and saves gas as compared to driving with the windows down,” Bennett says. “When the windows are up, the vehicle is more aerodynamic. When the windows are down, this creates excess drag on the vehicle, which increases resistance.”

What Are Some Ways to Improve Fuel Economy?

If you want to significantly improve your miles per gallon (MPG), forget about the AC. Look elsewhere. AAA has plenty of tips online, but here are a few to note.

• Tire pressure: “Having tires that are improperly inflated will have more impact on gas mileage than whether the AC is used or not,” Bennett says. “Overinflated tires are less of an issue, but underinflated tires have a higher rolling resistance, which reduces fuel economy.”
• Drive conservatively. Avoid rapid acceleration and hard braking. AAA notes that can lower fuel economy by 15 to 30 percent at highway speeds and 10 to 40 percent in stop-and-go traffic.
• Avoid excessive idling. If you’ll be stopped for a minute or more and if it’s safe to do so, shut off your engine. An idling car consumes one-quarter to one-half gallon of fuel per hour.
• Proper vehicle maintenance: To improve fuel economy, consumers should maintain their vehicle according to the manufacturer’s recommended service schedule.

Next: Learn why car AC doesn’t blow cold air sometimes and how to recharge your car’s air conditioner.