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Air Conditioning and Fuel Efficiency

Fuel Efficiency and Climate Control: Can the Two Coexist When Driving?

The short answer is yes, they can…sort of. The long answer is, it depends on where you draw the line between efficient and inefficient.

The answer also depends on the type of vehicle, temperature, and condition of your AC system.


First, let’s consider the alternatives

Fuel consumption does not dramatically increase the moment you switch on the AC. However, because automotive AC units rely on the engine for power, the engine does have to ask a little more of the gas tank to maintain its speed.

But, let’s start by putting fuel economy in perspective. Yes, air conditioning diminishes your overall MPG. There’s no way around it.

What are the alternatives on a hot day? Walk? Bus? Windows down? Air vent? Hitchhike? All but one of these options are great ways to avoid unnecessary spending at the pump.


The windows-down myth

Far too many drivers believe that rolling the windows down is both earth-friendly and economical. The sad truth is that it’s neither.

Driving at highway speeds with the windows down, neglecting a perfectly healthy AC system actually creates drag as air forcefully hits the back windows.

A study was done by the Society of Automotive Engineers (SAE) in 2004, finding that fuel consumption increased 20 percent while driving an SUV at 50mph with the windows down. Consumption increased only 10 percent while driving the same car at the same mph with the windows up and the AC on its coolest setting at medium speed.

The truth about fuel economy and air conditioning

For the best of both worlds – fuel economy and a comfortable ride, be tactful about when and how you use your air conditioning.


Auto Air Conditioning and Fuel Economy

Tactfully Using Your AC to Increase MPGs

Here’s a quick guide to maximizing fuel efficiency and staying comfortable in the car when it’s warm outside:

  • Keep Moving – Remember that automotive AC compressors work best when the vehicle is in motion
  • Cool Down the Hot Seat  – To cool the car down when you first get in, open the back windows and turn on the fan
  • Lower Speed, Lower Windows – Keep the windows down at slower speeds
  • All Systems Go – Use the air conditioner if you’re traveling faster than 50mph
  • Go All the Way – Keep the temp all the way down. Most systems automatically cool the air to around 38 degrees. Increasing the temp at the dial actually demands that the system re-heat the air. This obviously requires more energy/fuel
  • Clean it Out – Keep the air filter clean for better air flow
  • Stop by the Shop – If the air is warm or inconsistent, have your system looked at by a local shop, like Federal Way Automotive, that specializes in automotive air conditioning