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Impact of AC on fuel efficiency of a car: myth vs reality

One of the most unsolicited pieces of car advice you can get is to turn off the AC and roll down your windows; you’ll get better gas mileage out of your car. Nearly everybody knows and acts on it; it’s like a piece of conventional wisdom that will exist as long as humans keep driving. However, is there any reality to the impact of AC on fuel efficiency, or is it just an adage that, like most popular adages, is worldwide without any substantial evidence to prove it? In this blog, we’ll try and answer this burning question once and for all: whether or not AC impacts a car’s fuel efficiency. 

Owning a car and running it, especially if the person thinks of their vehicle as simply a machine to take them from point A to point B, all boils down to making it an efficient vehicle. This means that the fuel economy should be something that is affordable and does not mean financial ruin. With gas prices always fluctuating and summers getting unbearable, ACs are more of a necessity than a luxury, which is why people are getting increasingly interested in the impact of ACs on fuel efficiency. 

Let’s consider whether AC and its relation to fuel efficiency is a myth or a fact. 

Impact of AC on fuel efficiency: myth or reality?

Let’s keep things simple first and then move on to the complex explanations. YES, AC does have an impact on fuel efficiency. It is not a myth; this is a tested fact. AC reduces the fuel efficiency of a vehicle, but just how much depends on several factors, which will be discussed after we look at how this happens. 

So, an air conditioner in a vehicle, whether diesel, gasoline-powered, or electric, runs on the simple principle of heat exchange. This is done by a compressor that is usually located in the engine bay, right behind the grill of a car (in conventional internal combustion engines or ICE-powered vehicles). This compressor not only has to bring down the cabin’s temperature in summer but also regulates the temperature of the internals as well, given the extreme heat being generated from the engine into the bay, which takes up quite a lot of energy. 

Why AC impacts fuel efficiency negatively?

Given that the compressor requires a lot of energy to perform its functions adequately, the compressor is connected with a belt to the crankshaft of the engine, which itself is responsible for moving the driveshaft, which, as the name implies, drives the car. Since the camshaft now has to work extra to drive the car, maintain its power levels, and drive the AC compressor belt, this also taxes the engine, which has to consume more to do the same job. Which causes it to consume more fuel, decreasing fuel efficiency.

However, the decrease in fuel efficiency is not a lot; it’s not like the tank of gas that you just brimmed would be halved in a matter of hours. No, the impact is less significant and, again, depends on a number of factors. But before we look at the factors, lets discuss briefly how much the impact is on fuel efficiency. 

How much does AC impact fuel efficiency?

As explained beforehand, the fuel efficiency of a vehicle isn’t impacted much by the usage of the AC. The other factors punch a really big hole in the fuel economy. A test was conducted by Consumer Reports, which used a normal Honda Accord sedan and a Toyota Tundra pickup truck to test the impact of AC on car mileage. The results are as follows, 

  • For the Accord sedan, the AC caused the fuel mileage to drop by 3 per cent instead of keeping it off and rolling down the windows. The vehicle was doing a stable 65mph throughout the test, and the effect, as you can see, was minimal. 
  • For the Tundra pickup, the fuel economy went down by 10 per cent, being driven at a constant 65mph with the AC on. With the windows rolled down, the truck did not experience significant drag, which could affect the fuel consumption. 

Trucks have bigger cabins than your regular sedan, which is why the AC compressor has to work hard to keep it cool, therefore explaining the 10 per cent drop for the pickup truck. 

Factors affecting the fuel efficiency with the AC on

Other factors also play in the equation, which may work alongside the AC to reduce fuel economy further. Here is a quick explanation of some of them. 

  • Vehicle type: The vehicle type will determine how much the drop in efficiency will be. From the abovementioned example, sedans and small hatchbacks experience the least drop in fuel efficiency. In contrast, big trucks, SUVs, and full-size pickups experience the most since the cabin takes much more cooling to keep the occupants. 
  • Driving style: While the engine may experience a power drop with the AC on, this effect is noticeable on vehicles with engines less than 1800ccs of displacement. The performance drop is barely noticeable for engines of and above 2 liters. However, driving aggressively will consume even more fuel, which will substantially drop the fuel economy. Driving mildly with the AC on will not affect the consumption numbers much. 
  • Engine condition: The car’s fuel efficiency also generally depends on the engine’s condition, whether it is new or old and inefficient. With the AC on and the engine getting taxed even further, this will tank the fuel efficiency even more, and if the engine is new, the fuel efficiency drop will be barely noticeable. 

Tips to improve your fuel economy with the AC on

It is established that AC affects a car’s fuel economy, causing it to drop down, either massively or fractionally. However, that does not mean you must sit in the sweltering heat without AC to save on gas. Follow these tips, and your car will stay efficient. 

  • Drive sensibly. Sudden acceleration, hard braking, and long periods of a buried gas pedal will only make the fuel economy worse. Try to curb the Schumacher inside you until you don’t need the AC.
  • Ensure your tires have enough air pressure. Deflated tires increase rolling resistance when the engine has to work extra since the wheels aren’t inflated properly. Rolling resistance can affect fuel efficiency and cause it to drop significantly. 
  • Always top up with good quality fuel. Filling up your tank with low-quality fuel will affect the internals, affecting the performance and health of the engine. Bad fuel clogs the internal parts like fuel pumps, whereas good fuel cleans it. 

The bottom line

Driving during summer can be a problem; you don’t want to spend extra on gas, but neither can you sit at the lights with your cabin baking. This is why many people alternate between repeatedly switching the AC on and off, which unnecessarily stresses the engine. Following the aforementioned tips, you can enjoy the AC in your car without paying an arm and leg for gas. 

Magnum Autoclub: for your car to feel new again

Magnum Autoclub treats your car to a special level of care, making it feel like new again. For those of us who treat our cars like the machine that gets them from point A to point B, they can get a bit hairy, and maintenance for our cars is something that eludes most of us. However, Magnum Autoclub returns that new car feels to you and treats your car to another level of care. From engine maintenance to tires, oil, and fluid top-ups, Magnum gets your car to the next level. Trust us with your car, and get ready to drive home in a brand-new-feel car. 

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