How is the Fuel Efficiency of a Car Tested?

Car Fuel Test

Majority of the people around the world prefer to buy fuel efficient cars. However, many complain that their cars don’t give as much mileage as mentioned by the car manufacturers. A friend of mine bought a Suzuki Swift, and complained that his car doesn’t do 10-14 KM/L as claimed by Suzuki.

The reason why cars don’t give the mileage listed by their manufacturers, is because the mileage is tested under controlled laboratory conditions. In some countries, the test is conducted continuously for 20 minutes.

The test is split into two cycles, Urban and Extra-Urban Cycle. The Urban Cycle covers 67% of the test, while the extra-urban cycle covers 33%. In the urban cycle, the car is tested in conditions that simulate driving in a city. The car is made to do an average speed of about 19 Km/h with stops and idle periods.

Urban and extra urban test

In the Extra-Urban Cycle, the car is made to run at an average speed of about 60 km/h with peak speeds of about 120km/h. This test is carried out to simulate driving on a highway, though it isn’t accurate because the tests are conducted on controlled speeds and for a period of time.

Below is a checklist of a few things that car manufactures check before conducting these tests:

  • Tyre pressure and oil viscosity (vary for different car manufacturers)
  • Lights and signaling devices are switched off
  • The tests are conducted between 20-30 degrees Celsius temperature
  • Fuel density is checked (in a few cases)

The reason why a car’s mileage is different from the one claimed by manufacturer includes the factors like, wind, extra weight, air condition and other variables that affect the car on the road. These variables are not taken into account during the laboratory test. This why, real life mileage differs from the mileage indicated by manufacturers.

Do share your experience on the fuel efficiency of your car. Does the manufacturer of your car satisfy your expectations?


Samiullah Sharief

Samiullah Sharief is a car enthusiat. He is passionate about writing blogs and reviews about cars. His hobbies are driving,watching TV Shows like Top Gear, Mega Factories and he follows Popular car magazines. You can reach out to him by tweeting @sami649

  • Kamran malik

    In some test they go so far that they even remove side mirrors to effect aerodynamics.

  • The car in a laboratory test is stationary, the test is being done on rolling road. Removing the side mirrors is pointless. In real world testing conditions where cars are being driven on the road, no one removes the side mirrors – it is both dangerous and illegal.

  • Kamran

    Well I read somewhere about this, I think it was Volkswagen. Will give u reference if I found it.

  • I guess what you read about was the testing of prototype cars like the Volkswagen XL1 which is now in planned production. These cars are usually designed without side mirrors, they have cameras instead that project the rear images on the in dash screen. Others use panoramic rear view mirrors (the mirror inside the car, fixed on the roof in the center) instead of regular ones that give a large view but that view may be obstructed if one has passengers.