7 reasons why the real world fuel efficiency of your car rarely matches the ARAI certified figures

Snapshot: The Automotive Research Association of India (ARAI), a premier automotive testing body run by the Government of India tests every single automobile sold in India for emissions by putting the vehicles through what is known as the Indian Driving Cycle (IDC). While doing so, the fuel efficiency of the vehicle is also calculated by an empirical formula. Most car makers happily advertise the ARAI certified mileage figures of their cars as these figures are usually the best possible mileage that the car can give on Indian roads. 

Misled by fast talking car salesmen, most Indian car buyers who buy a car thinking that it will deliver the same mileage as promised by the ARAI certified figures are a disappointed lot. Other car buyers actually claim that they manage to beat the ARAI claimed figures by hypermiling (What is Hypermiling?), much to the surprise of their peers. Why this seeming difference in fuel efficiency numbers from the real world and the ARAI certified ones advertised by the car makers. CarToq gets to the bottom of the ARAI testing procedure, or the IDC to explains. 

ARAI’s mandate is to not test fuel efficiency at all

The IDC test that ARAI conducts on all automobiles sold in India is to measure emissions and ensure that automobiles meet emission standards enforced in India. The emission test also allows fuel efficiency to be measured by an empirical formula. Marketing departments across car makers love nice mileage figures and they’re more than happy to release the best possible fuel efficiency their respective cars manage under the IDC conditions. ARAI, for its part, released this information to allow car buyers to compare between mileage figures across different cars. So, the ARAI figures are meant to know which car delivers more mileage and which cars delivers less mileage, certainly not to “represent the mileage that a car will give under normal road conditions“. One can’t really blame ARAI in lieu of a bunch of enthusiastic marketeers at car companies.

Enter the Standard Test Conditions


The ARAI emissions/mileage test is done under standard testing conditions that aim to simulate the Indian Driving Cycle (IDC). In this test, the average speed of a car is about 31 Kmph. Both city and highway conditions are simulated but the test conditions are a far shot from the rear world conditions which include high periods of idling at traffic lights, starting and stopping and also different weather and road conditions. For instance, the fuel efficiency of a car at sea level will be much different to what that at 10,000 feet above sea level, where the elevation, humidity and temperature levels are quite different. ARAI simply doesn’t consider these variable conditions through its IDC test.

Air conditioning switched off

Can you live without air conditioning in a city like Delhi, Mumbai or Chennai? Well, the ARAI IDC doesn’t consider air conditioning when computing the fuel efficiency of a car. Since the test’s main purpose is to test emissions and not fuel efficiency, air conditioning simply doesn’t exist in the ARAI tester’s scheme of things. So, the ARAI certified mileage figures miss out a crucial detail such as air conditioning, which is a standard fixture in most real life driving conditions.

Car tested on dynamometer, not on actual road

The ARAI IDC emission/mileage test is conducted on a chassis dynamometer and not on a real road. Although the test does go to a great length to simulate real world conditions by considering inertia and other forces that act on a car and impact fuel efficiency performance, the real road cannot be simulated perfectly in lab conditions. So, you are actually reading mileage figures of a car that sits stationary on a dynamometer but with its engine and tyres moving.

Driving style varies

ARAI tests are carried out in conditions where a computer monitors the throttle, clutch and brake positions. The test involves no steering at all. In other words, it is as standardized as possible like it should be to measure emissions of different cars. In the real world though, each driver drives differently. And it is this difference that manifests itself into different mileage figures at the end of the day. So, when you have one driver claiming 25 Kmpl from a Honda Amaze and the other managing only 22 Kmpl from the car under similar driving conditions, you now know where these figures are coming from.

All tests conducted on brand new cars

ARAI conducts tests on brand new cars, which means that wear and tear of parts are inconsequential. While your new car might deliver great mileage, it might not manage the same after a few thousand kilometers. This factor is actually lost on the fuel efficiency numbers which brings us back to the purpose of the test. The test is not designed to measure fuel efficiency but tail pipe emissions.

Test carried out over limited distances, in under 20 minutes

The ARAI IDC test lasts for 1,140 seconds or 19 minutes. during the test, the car covers 10 kilometers on the dynamometer, across “simulated” city and highway road conditions. Average speed is 31.6 Kph with the maximum speed not to exceed 90 Kph at any given point of time with gradual acceleration and deceleration being the key. So, is 10 Kms a representative of all that you and your car go through on Indian city roads and highways? Well, you know the answer, don’t you!