Vehicle fuel consumption often exceeds official WLTP figures due to factors such as terrain, driving style, use of air conditioning and vehicle weight. This discrepancy can be frustrating for French motorists keen to control their fuel costs.
The WLTP cycle: a more realistic but imperfect standard
The WLTP (Worldwide Harmonized Light Vehicle Test Procedure) is a test protocol introduced in 2017 to measure the fuel consumption and emissions of vehicles. This standard replaces the old NEDC cycle, which was considered too far removed from real-world conditions of use.
The WLTP aims to provide more accurate data by reproducing varied driving conditions. It takes into account different driving styles, speeds and road types. Despite these improvements, gaps persist between the approved values and the consumption observed by users in everyday life.
The impact of relief on consumption
The topography of the terrain plays a crucial role in fuel consumption. WLTP tests cannot faithfully reproduce the diversity of landscapes that French drivers encounter on a daily basis. The winding roads of the Alps or the hills of the Luberon demand more from the engine, leading to higher consumption.
In mountainous regions, constant climbs put a lot of strain on the engine, significantly increasing consumption. Conversely, descents reduce consumption thanks to engine braking, but do not fully compensate for the increased consumption of climbs.
The influence of driving style
Every driver has their own way of driving, which directly impacts fuel consumption. Sudden acceleration, sudden braking and driving at high speeds significantly increase consumption compared to the standardized conditions of the WLTP cycle.
Aggressive driving in the city, with many stops and starts, can increase consumption well beyond the announced figures. Conversely, smooth and anticipatory driving on the highway allows you to get closer to the approved values, or even improve them in some cases.
Air conditioning use: an often overlooked factor
The use of the air conditioning system has a significant impact on fuel consumption, an aspect rarely taken into account in official tests. During the summer heatwave, intensive use of air conditioning can increase consumption by up to 20%.
In winter, heating and demisting systems also draw on the engine's resources. These features, which are essential for comfort and safety, are generally not activated during WLTP tests, creating an additional gap with real consumption.
Vehicle weight: a determining factor
The mass of the vehicle directly influences its fuel consumption. WLTP tests are carried out with a standard weight that does not always reflect the reality of daily use. Luggage for holidays, additional passengers or the addition of a towbar increase the total weight and, therefore, consumption.
Each additional kilogram requires more energy to move the vehicle, especially during acceleration phases. A loaded vehicle will therefore consume more than what is announced in the official figures, based on standardized test conditions.
Weather conditions: a variable factor
Climate conditions also influence fuel consumption. Extreme temperatures, whether it is the summer heat of the South of France or the winter cold of mountainous regions, affect engine performance and vehicle aerodynamics.
In cold weather, the engine takes longer to reach its optimum operating temperature, which increases consumption on short journeys. Inclement weather such as rain or snow increases rolling resistance and can also lead to excess consumption.
Vehicle maintenance: an often neglected aspect
The general condition of the vehicle plays an important role in its consumption. Underinflated tires, dirty filters or a poorly maintained engine can significantly increase fuel consumption.
Regular maintenance and careful attention to tyre pressure help keep the vehicle in a condition close to that of the WLTP tests. Neglecting these aspects can lead to significant and costly overconsumption in the long term.
Finally, it is essential to understand that the consumption figures announced by manufacturers mainly serve as a basis for comparison between different models. Actual consumption will always depend on multiple factors related to the specific use of each driver and the conditions in which the vehicle operates.