Is It Worth Driving Without AC For More Fuel Efficiency? Find Out Here

We performed 3 tests with the Toyota Glanza, the rebadged Maruti Baleno: AC on windows up, AC off windows down and AC off windows up

Fuel efficiency has been one of the top priorities for Indian car buyers and is still among the top three. The best conditions for most cars to be frugal is when cruising on highways at normal speeds. But there are a lot of people who think turning OFF the AC and pulling the windows down will boost their car’s mileage even further. So we decided to perform our own tests to see how true this practice is.

Parameters

We took the Toyota Glanza on this test, the cross-badged version of the extremely popular Maruti Baleno premium hatchback. It comes with a 1.2-litre petrol engine (90PS/113Nm) and our testing unit had a 5-speed manual transmission. We started out by fueling it up to the brim and then headed to the expressway. We performed 3 tests, drove for 81km each time, targeting an average speed of 100kmph and fueled up the Glanza after each test. 

Here are the results:

AC ON & Windows Up

Under normal driving conditions, we set the AC at 24 degrees Celsius and the fan speed to two. After covering 81km on the expressway, the Toyota hatchback used 3.74 litres of petrol. We calculated that in those conditions, the Glanza was giving a fuel efficiency of 21.66kmpl. Next, we repeat the process but with the AC off.

AC OFF & Windows Down

In our second test, we decided to do what many think can increase their car's mileage. We switched off the AC, pulled both the front windows down, and repeated the 81km drive at an average speed of 100kmph. After completing the test, turns out the Glanza was LESS efficient than with the AC ON.

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But how did turning the AC OFF reduce the mileage? The answer is aerodynamic drag. When driving on the highway at high speeds, the car is going against the air. Lowering the windows lets that air into the cabin and at high speeds, pushes the car in the opposite direction like a parachute. Due to this, the engine has to work more and generate more power to stay at the same speeds, which in turn burns more fuel and reduces the car’s mileage. 

Inside the city at lower speeds, however, the aerodynamic drag is not that much, so the engine does not have to work more and burn more fuel. So driving with the AC OFF and windows down inside the city can give you better fuel efficiency, though the opposite will occur when highway cruising. But what if we turned the AC OFF and kept the windows up?

AC OFF & Windows Up

This is exactly what we did for our third test. Making the most of our time in hand, we went for a third run. Same route, same speed, AC still off, but this time the windows were up. In the interest of occupant safety, and to not sweat so much, we set the blower speed to two.

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By removing the aerodynamic drag of the windows being open, we took some load off the engine. At the end of our tests, we got a mileage of 23.47kmpl, which was the best one by far.

Verdict

With our results, it's clear that turning the AC off and lowering the window does not save you much fuel on your highway drives, in fact, it ends up burning more. So it’s better to keep the AC on and windows up and enjoy your drives comfortably. You can do this inside the city where there is less aerodynamic drag since the speeds are lower.

But if you want to save some fuel while cruising on the highways, or extend the range of your EV to the nearest charging point, you can turn OFF the AC, only use the blower and keep the windows up, to get better efficiency from your car. Note, this technique is best reserved for cooler weather conditions and we do not recommend using it in high temperatures as that could lower the driver’s attentiveness over the journey.

Read More on : Glanza AMT