Vehicle fuel consumption often exceeds the 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 anxious to keep their fuel costs under control.
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 vehicle fuel consumption and emissions. This standard replaces the old NEDC cycle.cycle, considered too remote from actual driving conditions.
WLTP aims to provide more accurate data by reproducing a variety of driving conditions. It takes into account different driving styles, speeds and road types. Despite these improvements, there are still discrepancies between the approved values and the fuel consumption observed by everyday users.
The impact of terrain on fuel consumption
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 place greater demands on the engine, resulting in higher fuel consumption.
In mountainous regions, constant uphill gradients place heavy demands on the engine, considerably increasing fuel consumption. Conversely, downhill gradients reduce fuel consumption thanks to engine braking, but do not fully compensate for the higher consumption of uphill gradients.
The influence of driving style
Every driver has his or her own driving style, which has a direct impact on fuel consumption. Hard acceleration, hard braking and driving at high speeds significantly increase fuel consumption compared with standard WLTP cycle conditions.
Aggressive city driving, with numerous stops and starts, can push fuel consumption well beyond the advertised figures. On the other hand, flexible, anticipatory driving on the freeway can bring fuel consumption close to the approved values, and in some cases even better.
Air conditioning use: a factor often overlooked
The use of air conditioning has a significant impact on fuel consumption, an aspect rarely taken into account in official tests. During the summer heatwaveintensive use of air conditioning can increase fuel consumption by up to 20%.
In winter, heating and defogging systems also draw on the engine’s resources. This equipment, essential for comfort and safety, is generally not activated during WLTP tests, creating a further discrepancy with actual consumption.
Vehicle weight: a determining factor
Vehicle weight has a direct influence on fuel consumption. The WLTP tests are carried out using a standard weight which does not always reflect the reality of everyday use. Luggage for vacations, extra passengers or the addition of a towbar increase total weight and, consequently, fuel consumption.
Each additional kilogram requires more energy to move the vehicle, particularly during acceleration. A loaded vehicle will therefore consume more than the official figures based on standardized test conditions.
Weather conditions: a variable factor
Weather conditions also influence fuel consumption. Extreme temperatures, from the summer heat of southern France to the winter cold of mountainous regionsaffect engine performance and vehicle aerodynamics.
In cold weather, the engine takes longer to reach its optimum operating temperature, which increases fuel consumption on short journeys. Inclement weather, such as rain or snow, increases rolling resistance and can also lead to higher fuel consumption.
Vehicle maintenance: an often neglected aspect
The general condition of a vehicle plays an important role in its fuel consumption. Under-inflated tires, dirty filters or a poorly maintained engine can significantly increase fuel consumption.
Regular servicing and careful attention to tire pressure can keep your vehicle close to WLTP-test condition. Neglecting these aspects can lead to significant and costly over-consumption in the long term.
Finally, it’s essential to understand that the fuel consumption figures announced by manufacturers are mainly used as a basis for comparison between different models. Actual consumption will always depend on multiple factors linked to the specific use of each driver and the conditions in which the vehicle operates.
