Does Car Air Conditioning Use Gas?

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Does car AC use gas? Your friends at Ottobot Motors are going to tell you! Using AC in your car does more than just keep you cool. It can be used to help clear fog from your windscreen, and if you’re clever about it, running the AC can actually help stop your car from overheating in an emergency – if you know what to do. All of the tips and tricks that we’re about to reveal work in all cars, trucks, and SUVs. So read on with confidence! If you love what you’ve learned here, don’t forget to share this article with your friends or drop us an email to let us know!

Your Car’s Climate Control System Demystified

In order to understand the impact of AC or heat on your vehicle’s fuel economy, we need to take a look at how this system works. We’ll distill it down to the key players:

  • Climate Control Matrix – Different OEMs call this part many different names, but it’s a big plastic box inside the center of your dash, behind your radio, infotainment, and controls. It contains the flaps, ducts, and channels for your climate control system. It’s about the size of a full bag of groceries.
  • Blower Motor Assembly – This allows you to adjust your ventilation system’s speed. You can almost always hear the “whoosh” of the blower motor when you adjust the speed from your temperature controls. Most cars have one blower motor. Some higher-end vehicles have two or more.
  • The AC Compressor – Driven by the fan belt going around your engine, the AC compressor engages when you turn it on. It compresses a high volume of refrigerant and sends it flowing through secondary AC components towards your Climate Control Matrix.
  • Your Heater Core – This is a mini radiator inside your Climate Control Matrix. It circulates heated engine coolant through your vehicle. That warm air you feel with the heat on? Thank your engine. That’s where the heat is coming from (and also why you don’t have heat until your vehicle has “warmed up”).

So now that you have an understanding of the major players in your AC/heating system, we can better understand its impact (or lack of impact) on your car’s fuel economy.

Does Car AC Use Gas? Secrets Revealed

So we know that we have two separate systems (AC & heat) that pass through the Climate Control Matrix. You select your temperature, and your blower motor assembly pushes the air through your vents at the desired speed. So which one, if any, uses gas?

  • Does a car heater use gas? No. Remember, your heater is supported by warmed engine coolant. When your engine is spinning, the water pump drives coolant through the engine, radiator, and associated hoses. Then it’s driven into the heater core and back again. Your car will always have heat running through it due to this continuous flow. When you select heat, those channels open, and it makes its way into your vehicle.
  • Does air conditioning use gas? Yes. Why the AC and not the heat? Your AC compressor is spinning freely while the engine is running, and the belts are turning the pulley. In this state, it is otherwise invisible to the eyes of your engine, and there is no impact on fuel economy at this point. When you turn the AC on, a clutch (in older cars) or internal solenoid (newer cars) engages and becomes something “extra” that your engine needs to power.

Think of it this way. Turn on a treadmill and stand off to the side, watching the belt go around and around. You’re there in the room, right? But the treadmill just sends the belt around nice and easy. Then, surprise the treadmill and jump on it and start running. What happens? It immediately groans and slows down under the force of your weight.

Similarly, your AC compressor is just spinning freely, minding its own business until you turn it on. Then your engine has to deal with the weight (or “load” in mechanic terms) of all that compressed gas that just decided to hop on and go for a run. Check out our guide for buying used cars. Running the AC/heat is one of the best ways to check the health of any engine. If a vehicle’s engine has hidden problems, running the AC & heat will reveal them.

Tips & Tricks for Better Fuel Economy

Let’s say you’re taking your used Chevy to the levy on a warm summer month (because who goes in February anyway?). You’ll likely run your AC system to keep things cool, and as we’ve learned, running your AC does waste gas. So what can you do, if anything, to help keep your fuel economy going in the right direction? Here are some of our best tips for fuel economy:

  1. Drive like there’s an egg under the gas pedal. The gentler you are on the gas, the less your engine will waste it (which is a natural byproduct of over-fueling under acceleration).
  2. Make sure your tires are inflated. When filled to the specified inflation, your tires are designed to have minimal “rolling resistance.” The less air you have in your tires, the harder your engine will have to work to move you around. Having correctly inflated tires is like walking on a sidewalk. Low air in your tires is like trudging through snow.
  3. When in town, windows down. City driving involves a lot of stops and starts. This is tough on fuel economy because you’re constantly burning extra fuel to get going from a standstill. Running your AC can make matters worse. So if it’s not boiling outside and there’s a breeze, you can save a little on gas by not adding that extra load to your engine.
  4. Breathe the free air. Your engine has a few key air passages that allow a burst of air into the engine to offset the load created by your AC system. Make sure your air filter is clean, that you have no vacuum leaks, and that your throttle body and idle air control valve are free of gunk and build up.

Does Car AC Use Gas? You Tell Us!

Congratulations! You now have more technical understanding of AC system operation than many people in Dallas! For those of you who might have been wondering this whole time, let’s address this last question as a parting note. Does the size of your engine offset the load of your AC system? Yes. A little 4CYL engine will have to work MUCH harder to move all that refrigerant around than a monstrous 702-horsepower Dodge Hellcat engine. The Hellcat isn’t a vehicle you buy for fuel economy anyway, but that being said, its engine is SO powerful that when the AC is kicked on, it virtually makes no difference. Want to test that theory? What do you think would happen if you turned on that treadmill again, but this time to the maximum speed? Go ahead and jump on and see if it knows you’re there.

We hope that you have found this article useful. Of course, there are way more components involved in AC system operation, but this is the simplest way to understand how using a car’s AC affects fuel economy. Stay cool out there, Irving, TX!