Car Fuel Consumption Comparison: Differences Between NEDC, WLTP, EPA, and CLTC Methods

The real fuel economy is often lower than manufacturers declare. The thing is that there are several methods for measuring a vehicle fuel consumption. And each of them bears little resemblance to your daily trips, although they try very hard! At Indy Auto dealership, our team decided to review each of the tests in detail and select the one that most accurately reflects real-life experiences. 

Check our comprehensive car fuel comparisons before we start:

NEDC. Greetings from the 1970s

How to compare the fuel consumption of similar cars from different manufacturers? While it may be possible in theory to find a perfect driver to test all the different car models, in reality, the Standardized Driving Cycle is used instead. The driving cycle consists of a series of exercises designed to mimic real-world driving conditions, during which the amount of fuel consumed is measured.

Despite its name, the NEDC (New European Driving Cycle), which is used to collect fuel consumption data for most vehicles, is not actually new. The standard was developed for gasoline and diesel cars in the 1970s.

To conduct tests, you need a dyno stand with several rollers onto which the subject drives. The rotation of the tires is transmitted to the rollers, imitating the resistance of the road. A fan installed in front of the car creates a flow of oncoming air.

The test consists of four repeating cycles in the city and one "country trip". During the city test, the car accelerates, maintains the speed, and then brakes. And this happens three times in a row. The first acceleration is up to 15 km/h (9 mph), the second to 32 km/h (20 mph), and the last one is up to 50 km/h (31 mph). The maximum permissible acceleration is about 1 m/s2 ( 3 fps²). This is the same as accelerating to 30 mph in half a minute. Does this sound realistic?

During the simulated country trip, the car reaches 70 km/h (43 mph) in 41 seconds, maintains the speed, and accelerates to 100 km/h (60 mph). After that, there is another pause, and then it accelerates to 120 km/h (74 mph). All the accelerations in this test are not very dynamic. At the time of the methodology development, cars were not as powerful as today.

To measure the fuel consumption of petrol and diesel engines, a separate sensor "smells" the exhaust gases and determines their composition, and the computer calculates how much air enters the car and how much fuel it consumes. The result is the average value between the city and suburban tests.

For electric cars, they calculate the difference between the starting charge of the battery and the value after the test.

WLTP. New European standard

NEDC has long been outdated, so now there is a gradual transition to a new standard – WLTP (Worldwide Harmonized Light-Duty Vehicles Test Procedure). Since the 1980s, the preparation has been underway and has become mandatory for all vehicles in the EU, Norway, Switzerland, Iceland, and Turkey since 2019.

The basis is the same dyno stand and exhaust gas measurement. But now the test cycles depend on the weight-to-power ratio of the car. The more powerful the engine, the faster the acceleration, the higher the maximum speed, and the tests themselves last longer.

A total of three different classes were introduced. The speed test modes were also changed. For example, in the urban cycle, the maximum speed reaches 56.5 (35) and 76.6 km / h (48 mph), and in the extra-urban cycle - 131.3 km / h (82 mph). The maximum acceleration during the test is about 1.7 m/s2 (5.6 ft/s²). A car should have more than 34 watts of power per kilogram (15 watts/pound) to get under the toughest tests. For example, Skoda Rapid with a 140 hp engine, has 84 watts per kilogram (38 watts/pound).

Each car must be tested at the same ambient temperature, with special calibrations of the dyno and exhaust gas measuring tools. The authorities also introduced regulations on the type of fuel, which must change depending on the region where the car is used. The low beams must be turned on, and the air conditioner is on for some tests.

Consequently, the fuel consumption and driving range figures deteriorated by 12-25% compared to the old method. However, they are much more true to life.

EPA. The most impartial test

The US Environmental Protection Agency independently tests all light vehicles entering the market. For this, they use a dyno, exhaust gas measurements, and several scenarios: city driving tests from the 1970s, as well as highway driving and aggressive driving, which were added in 2008.

There is no division into classes. During the 11-mile city test, the driver makes about 23 stops and accelerations but does not move faster than 56 mph. And there is practically no speed maintenance; the technique resembles standard city driving: gas, brake, stop, and start over.

On the highway, stops are not provided at all. The car moves at no less than 28 and no more than 60 mph. The aggressive driving test involves several stops, a maximum speed of 80 mph, and an acceleration of 12 ft/s2.

An additional fuel consumption test is carried out with air conditioning at an ambient temperature of 90 °F. At 21 °F, the heater must be on in electric vehicles. After all, the lower the temperature outside, the lower the battery capacity.

As a result, measurements carried out according to the EPA methodology show higher fuel consumption relative to WLTP and a smaller, by about 11 percent, power reserve. And looking ahead, we can call this test the most truthful. However, this did not stop the Chinese regulator from inventing another measurement.

CLTC. Chinese methodology

Until 2019-2020, the NEDC test was popular in the Chinese market since it produced the highest numbers, which is good for marketing. The only thing that spoiled the picture was that the standard came from the last century. As a result, the "China Light-Duty Test Cycle" was developed.

It is similar to the European WLTC since it adheres to three stages: slow, medium, and fast driving. The tests also include full stops, and the maximum acceleration is significantly lower compared to modern European tests - 1.47 m/s2 (4.8 lb/s2).

• At the first stage, the speed does not exceed 40 km/h (25 mph). 
• At the second - the peak mark is about 80 km/h (49 mph). 
• At the same time, the maximum speed is much lower than in Europe and America - only 114 km/h (70 mph).

 In the Chinese test cycle, cars make many more stops than in other tests, as it considers Chinese road realities.

Therefore, the results of fuel (energy) consumption and power reserve in China are 15-25% more optimistic compared to those of the European standards.

To better understand the difference, let's take the Tesla Model 3 as an example. The Chinese website promises to travel 713 km (443 miles) on one battery, the European one - already 390 miles, and the American one - only 363 mi. The difference between the Chinese CLTC and the American EPA is as much as 80 miles!

Compare car fuel consumption in Indianapolis

Understanding these measurement systems helps our customers compare the fuel consumption of cars from different manufacturers. It’s important to consider the driving style, daily routes, and car condition, which influences fuel economy. When buying a used car, check its average indicators on the dashboard, as they show the real-life car's consumption of the previous owner.

Find your favorite model at Indy Auto Man! With 300+ used car models for sale, you can select an economical option, compare it with other brands, and test your favorites on the roads of Indianapolis already today.