Air Conditioner Fuel Consumption

AC vent

In early cars like the 70s Peugeot 504 and other cars before that era when car AC compressors were bulky and not very efficient, it is indisputable that using your car Air Conditioner while driving means parting with some extra liters of fuel.  But we are in an era when car compressors are better built and lighter. That doesn't mean they don’t require power from the engine to be driven as is most noticeable at low rpm like when the car is idling and you switch on the AC. The noticeable drop in rpm is mostly due to inertia.

So, your glasses are down and your AC is off so you can save fuel. I bet the only place you are going to save that fuel in today’s cars is ‘in your head, not in your fuel tank’. If your glasses are down and you are driving at speeds in excess of 80km/h (about 55mph), the inside of your car will be working like a big balloon or parachute to pull your car back as air flows in through the windows. This way, the engine will be working harder than it should to keep the car moving at this speed. The car is at its best aerodynamic form when the glasses are up, making it glide effortlessly through the air.

air flow around a car

You must have noticed that you seem to drive a little faster when your glasses are up. That is not just because you are sealed from exterior noise made by the wind as it slaps against the hood (burnet), windshield, and side mirrors, but also because the engine finds it much easier to push the car through the gears to a higher speed.

What if you are sitting in high traffic where you can’t drive fast to experience drag. You will save some fuel in this condition if you don’t use your AC. You can turn off your engine altogether so you don’t use any fuel at all. And if you are lucky to be driving one of these new cars equipped with cylinder deactivation technology , you don’t need to bother as your car will do just that for you.

But we are talking of sitting in traffic here. Would you rather sit in traffic with your glasses down, inhaling gas fumes from other peoples exhaust pipes and listening to people cursing? No! I suggest you wind those glasses up, hit that climate control button and hit play on your stereo. That way, you will pass the time quick and go home refreshed, instead of saving money in traffic to spend it on aspirin.
Read more on Car AC fuel consumption
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