Fuel Consumption Calculation

Calculating Fuel Consumption: The Guide for Professionals

For a fleet manager or professional driver, fuel is not just an expense, it is one of the main items in the total cost of ownership (TCO). Accurate fuel consumption calculations are therefore essential. Every liter wasted on a company car directly impacts your margins and the profitability of your business. This guide is designed to give you the keys to effective calculation, intelligent analysis, and, above all, to sustainably reduce the fuel consumption of your vehicle fleet.

How to Calculate Fuel Consumption? 

Calculating fuel consumption, expressed in liters per 100 kilometers (L/100 km), is the first step toward regaining control. Here are the most reliable methods.

The basic formula (L/100 km)

The universal equation remains the same, but applying it to an entire fleet requires great precision. The formula for calculating a car's fuel consumption is:

Fuel consumption (L/100 km) = (Number of liters of fuel consumed ÷ kilometers traveled) × 100

The fill method: a full-scale test

Using the fill-up method is a good way to check the actual fuel consumption of a specific vehicle:

1. Fill up the tank completely.
2. Drive the usual routes over a significant distance.
3. When refueling again, note the exact number of liters added and the number of kilometers traveled.
4. Apply the formula to obtain the actual fuel consumption of the car over this period of several hundred kilometers.

Although effective for a one-off audit, this method quickly becomes time-consuming and prone to error when applied to an entire fleet.

Use an online calculator 

Many websites and mobile apps offer automatic calculators. Simply enter the number of liters and the distance to instantly obtain your fuel consumption, saving you from having to calculate it manually.

Factors Influencing a Professional Fleet

Beyond the basics, a fleet manager must analyze complex variables that directly impact costs.

• Driving behavior: This is the number one factor. Sudden acceleration and braking, excessive idling, and inappropriate speed can increase fuel consumption by more than 30%. Good driving habits are essential to controlling overall costs.
• Vehicle type and use: The fuel consumption of a light commercial vehicle varies greatly depending on its load and engine type. The type of fuel (gasoline, diesel, biofuel such as ethanol) also has a direct impact.
• Route optimization: A non-optimized urban route, with frequent stops and detours, is a financial drain that increases the cost of each vehicle.
• Vehicle maintenance: A clogged filter, improper tire pressure, or an undetected defect in a combustion engine increase fuel consumption and the risk of breakdown.

Interpreting Your Fleet's Consumption Data

Comparing vehicle performance is a key driver of optimization. To do this, it is essential to have a performance benchmark tailored to each segment of your fleet. The following table shows the estimated average fuel consumption for each segment, as well as the key variables to monitor.

Category	Vehicle Type	Main Engine Type	Typical Use	Average Fuel Consumption (L/100 km)
Company Vehicles	City Car / Multi-purpose	Gasoline, Hybrid, Electric	Sales visits, urban travel	5 - 8 L/100 km
	Sedan / Station wagon	Diesel, Plug-in hybrid	Major highways, long journeys	5 - 7 L/100 km
Light Commercial Vehicles (LCVs)	Van (< 5m³)	Diesel, Electric	Courier, breakdown service	7 - 9 L/100 km
	Compact Van (5-12m³)	Diesel	Crafts, parcel delivery, construction	8 - 11 L/100 km
	Large Van / Chassis Cab (>12m³)	Diesel	Moving, large-volume transport	11 - 14+ L/100 km
Heavy Goods Vehicles (HGV)	Forwarder (12-19t)	Diesel	Regional distribution, heavy courier service	22 - 28 L/100 km
	Tractor Truck + Semi-trailer (40-44t)	Diesel	Long-distance transport (domestic/international)	28 - 35+ L/100 km

Please note: these figures are market averages. Higher consumption in one of your vehicles is not necessarily an anomaly. It may be explained by specific operational factors: a higher payload, more demanding route topography, a driving style that needs improvement, or the use of auxiliary equipment (such as a refrigeration unit). This is precisely where a tool like Dadycar becomes indispensable for tracking these discrepancies, understanding them, and correcting them.

Our Tips for Reducing Fuel Consumption

Move from simple observation to an active strategy for reducing consumption. The goal is simple: drive more miles on less fuel.

1. Train drivers in eco-driving: Set up programs to teach good driving practices: anticipation, accelerator management, use of engine braking.
2. Implement a preventive maintenance plan: Regular maintenance ensures optimal fuel consumption and helps control maintenance costs.
3. Optimize loading and equipment: Every extra pound in a service vehicle has a direct impact on the final bill.
4. Plan routes intelligently: Use tools to identify the shortest and smoothest routes.

Dadycar: The Fleet Management Solution to Control Your Fuel Costs

For a fleet manager, the key is to move from approximate tracking to precise control. Dadycar acts as a true assistant: it automates calculations, centralizes data, and transforms it into concrete levers for profitability. Much more than just software, it is a comprehensive fleet management platform.

• Data Centralization and Automation: Dadycar links every fuel card, refuelling and charging session to the right vehicle, and collects mileage automatically through telematics (connected vehicle or device). You have the liters and kilometers needed to calculate L/100 km, without re-entering data.
• Detailed Reporting and TCO Analysis: View fuel costs per vehicle or driver with a single click. Our dashboards let you track fuel spending and total cost of ownership per vehicle, with filters by site and period.
• Fuel and vehicle alerts: a tank level that drops with no trip triggers a fuel theft alert, and vehicle alerts with adjustable thresholds (engine warning light, fault codes, tire pressure) flag a mechanical problem before it becomes costly.
• Driving Behavior Analysis: Identify the best drivers and those who need support. With objective data on their driving, you can set up targeted training.

FAQ: Frequently Asked Questions from Fleet Managers

What is the difference in fuel consumption between the different engines?

For equivalent use, a diesel vehicle consumes on average 15% less fuel than a gasoline vehicle. A modern combustion engine, whether gasoline or diesel, is optimized for a certain type of journey.

How can I reduce my fleet's gasoline or diesel consumption?

Implement a comprehensive strategy: train your drivers, ensure rigorous maintenance, optimize routes, and use a tracking tool to measure progress.

How do you calculate the total cost of a trip for a company vehicle?

Multiply the vehicle's average fuel consumption (in L/100 km) by the distance traveled (in hundreds of km), then multiply the result by the price of fuel per liter.

Which commercial vehicles consume the least fuel?

Hybrid and electric versions perform well. For a combustion engine car or light commercial vehicle, the choice should be made based on usage to avoid excessive fuel consumption.