In short: fuel consumption is reduced in two steps. First you measure it accurately, with a fuel level sensor fitted in the tank, with data read from the vehicle's CAN bus or with a flow meter on the fuel supply line. Then you eliminate the sources of waste one by one: aggressive driving, idling, low tire pressure, load and aerodynamics, inefficient routes and deferred maintenance. Below you will find the 8 monitoring solutions, a comparison of the measurement technologies, the factors that drive up consumption, a practical step-by-step plan and the method for checking whether the savings you achieve are real and not just an impression.
Want the figure for your trip? Use the fuel consumption and cost-per-kilometer calculator — includes diesel, AdBlue and road tolls, with different consumption for the outbound and return legs.
Fuel consumption accounts for 60% of a fleet's total costs. As the biggest expense in running a fleet, it is often a challenge for managers to monitor the consumption of fuel. High fuel consumption can significantly increase a fleet's expenses and hurt operational efficiency.
The current situation regarding rising fuel prices makes controlling fuel costs an even bigger challenge. Sudden fuel price increases have affected virtually every company.
Companies with a vehicle fleet made up of several cars or heavy-duty vehicles have recorded negative results compared with their planned budget.
Fuel is an indispensable resource in transport, being one of the largest and most important running costs. Any change in fuel prices can have a major impact on transport companies.
To make fuel consumption more efficient and cope with these cost increases, fleet managers have to find effective solutions and adapt to the situation so that it does not disrupt the smooth running of operations. Digital solutions are the fastest, most reliable and most cost-effective alternative.
GPS monitoring equipment, monitoring driver behavior behind the wheel, recording fuel consumption and the reports these provide are the safest and most effective ways to reduce fuel and fleet management costs over the long term.
Fuel Consumption Monitoring Solutions
The 8 solutions below cover the situations in which fuel is actually lost in a fleet. You don't have to apply them all at once: if you start with the first three, you will already see where the liters are going.
1. Monitoring unauthorized vehicle use
It often happens that drivers use vehicles for personal purposes. That's why it is important to use a monitoring system that helps you see when the vehicle leaves a predefined area or is used outside working hours, avoiding extra fuel consumption.
2. Avoiding idling with the engine running
Fuel consumption can also be reduced by switching off the engine when the vehicle is stationary.
When the vehicle is stationary with the engine running, it causes unnecessary expenses and carbon emissions. Restarting the engine uses the same amount of fuel as 30 seconds of idling.
A monitoring system lets you see how long the vehicle has been running with the engine on so the driver can be reminded to switch off the engine, even for short stops.
3. Avoiding vehicle overloading
Overloading the vehicle increases fuel consumption, accelerates wear and can create safety issues for the driver and the vehicle.
It may sometimes be tempting to load more cargo, but this can have unpleasant consequences.
4. Monitoring the driver's driving style
The way drivers use vehicles is another important factor that can affect fuel efficiency. Monitoring drivers' driving style behind the wheel is therefore a solution that can cut some of the unnecessary fuel consumption.
Using monitoring equipment, you can record certain events such as harsh braking, hard acceleration and speeding above the legal limit.
5. Regularly checking maintenance work
Vehicles need to be checked to make sure they are always ready to run at full capacity, as otherwise fuel consumption can be affected.
This is easier with a monitoring system that notifies you whenever maintenance work is due (e.g. general service, oilchange, tire change, brake component replacement, etc.).
6. Checking tire pressure
If tire pressure is too low, rolling resistance increases and so does fuel consumption. This causes excessive fuel consumption that can vary depending on how much pressure is in the tires. Driving on “flat” tires increases fuel consumption by at least 4%.
7. Improving the vehicle's aerodynamics
It is best not to keep the windows open on the highway, as your vehicle loses aerodynamic efficiency. Fuel consumption will be 5% higher. At low speeds in the city, you can leave the windows open, since this does not have as much impact on fuel consumption.
8. Using fuel level sensors to reduce fuel consumption
The fuel level sensor for fleets is an effective solution that helps monitor fuel consumption and cut fuel costs by up to 25% every month.
It is seen as one of the most accurate and reliable solutions for making fuel consumption more efficient.
The fuel level sensor measures the fuel level in the tank, whether stationary or in motion. It can be installed very easily in the tank, on any type of vehicle, with one or two tanks.
Any deviation from normal consumption can be eliminated with a fuel level sensor. It can detect significant drops in the fuel level in the tank.
Fuel siphoning is completely eliminated, fuel consumption and refueling are monitored in real time, and significant drops in the fuel level in the tank can be detected.
If you want the full technical details of this equipment, you will find them explained at length in the dedicated guide: fuel level sensors and fuel consumption monitoring.
How fuel consumption is measured: the 3 technologies and how they differ
Before you can reduce fuel consumption, you need to measure it accurately. Pump receipts and the dashboard gauge only give you a rough average that hides exactly what you're interested in: where and when fuel is lost. Three technologies are commonly used, and the difference between them is not “which is better” but what each one actually measures.
The fuel level sensor (probe) (the level sensor in the tank)
The fuel level sensor is a probe mounted vertically in the tank that measures the fuel level over its entire height and sends the readings to the GPS unit. The continuous level graph yields three pieces of information that no other method provides as clearly: the time and quantity of each refueling, the actual consumption on each trip, and sudden level drops that can't be explained by mileage.
It is the benchmark solution for trucks, machinery and vehicles with large tanks, because it shows the difference between “how much you paid for” and “how much actually went into the tank.” The critical step is calibration: without it, level readings don't translate into actual liters.
CAN bus / FMS data read from the vehicle
Modern vehicles calculate fuel consumption internally and make it available on the onboard electronic bus (CAN bus), or on the FMS interface in trucks. A reader module connected to this bus directly retrieves total consumption, idle consumption, engine speed, vehicle speed, accelerator pedal position and fault codes, without any modification to the tank.
The advantage is quick installation and a wealth of driving-style parameters. The limitation: you see what the vehicle reports, not what is physically in the tank. Diesel theft does not show up in CAN data, because the engine never consumed that fuel. That's why, where theft is a real problem, CAN bus data is used together with the fuel level sensor, not instead of it.
The flow meter (instant consumption meter)
The flow meter is installed on the fuel supply line and measures the volume actually flowing to the engine, often on both the supply and return lines, with the difference being the actual consumption. It is the most accurate method for instantaneous consumption and is used mainly on machinery, generators, refrigeration units or stationary engines, where consumption doesn't correlate with distance traveled.
The drawbacks are more complex installation, higher cost and the fact that it says nothing about how much fuel is left in the tank: a flow meter shows perfectly normal consumption even when dozens of liters are missing from the tank.
| Technology | What it measures | Detects theft | Best suited for |
|---|---|---|---|
| Fuel level sensor (probe) | Actual level in the tank | Yes | Trucks, machinery, mixed fleets |
| CAN bus / FMS | Consumption reported by the vehicle, idling, driving style | Not | Newer vehicles, behavior analysis |
| Flow meter | Fuel reaching the engine | Partially | Machinery, generator sets, stationary engines |
The combination that covers most situations is a fuel level sensor for the tank level plus CAN data for driving behavior. The first shows you whether you are losing fuel; the second shows you why you are using more than you should. We have written at length about how this data uncovers refueling irregularities in our article on fuel fraud detected with a fuel level sensor.
What factors increase fuel consumption
Above-normal fuel consumption almost never has a single cause. Usually several small factors add up, each seemingly insignificant, which together visibly change the average per 100 km.
Driving style
It is the factor with the biggest impact and, at the same time, the only one that can be corrected without any investment in the vehicle. Hard acceleration, harsh braking, running at high RPM and constantly exceeding the speed limit increase fuel consumption significantly. Two drivers in the same truck on the same route can have different fuel consumption simply because of how they use the pedal and the gearbox. An EcoDrive module scores each trip based on these events, and the score becomes a data-driven discussion tool rather than one based on impressions.
Idling
An engine running while the vehicle is stationary burns fuel without covering a single kilometer. Prolonged morning warm-ups, waiting at the loading dock, waiting at customs or running the cab air conditioning during breaks add up by the end of the month to entire hours of unnecessary running. Idling is shown separately in reports, so it is easy to measure, and it is usually the first saving achieved after installing a monitoring system.
Tire pressure and condition
Underinflated tires increase rolling resistance, and therefore fuel consumption, in addition to uneven wear and the risk of a blowout. Checking cold tire pressure monthly and before long trips is the cheapest way to reduce fuel consumption. The type of tire matters too: low rolling resistance tires use less fuel.
Aerodynamics and load
At highway speeds, air resistance becomes the main force the engine has to overcome, and anything that disrupts airflow is paid for in liters: deflectors not adjusted to the height of the semi-trailer, loose tarpaulins, roof racks or brackets left fitted for no reason, open windows. Unnecessary weight, including equipment kept permanently in the vehicle, has the same effect with every acceleration.
Routes, traffic and unplanned stops
Extra kilometers always cost you. Routes chosen out of habit, detours, frequent stops and avoidable traffic jams increase both fuel consumption and delivery time. A tracking system shows the vehicle's position in real time, lets you redirect it to less congested routes and highlights repeated deviations. This data is also the starting point for an accurate calculation of the price per km in freight transport, because without actual fuel consumption you have no actual cost per trip.
Technical condition and fuel theft
A clogged air filter, dirty injectors, degraded oil, dragging brakes or a postponed service all translate into consistently higher fuel consumption on every trip. And when consumption rises suddenly with no technical explanation and no change in routes, the cause may be a fuel leak or theft; this topic is covered separately in the guide on preventing and monitoring fuel theft.
A practical step-by-step plan for reducing fuel consumption
Order matters. If you start with discipline measures before you have data, you will never know what worked.
- Set your baseline. For 4-6 weeks, before making any changes, record for each vehicle the liters refueled, the kilometers driven and the average consumption per 100 km. Without this baseline, any later savings remain a guess.
- Install the measurement system. A GPS unit on every vehicle, a fuel level sensor where the tank is large or exposed, CAN data where the vehicle makes it available. Calibrate the sensor and check the first refueling by comparing the receipt with the level increase on the graph.
- Identify the three biggest losses. The first reports immediately show where you're doing badly: idling hours, trips with a low EcoDrive score, discrepancies between refuelings and tank level, kilometers driven outside working hours. Don't tackle everything at once.
- Work with drivers, not against them. Present the data transparently, explain what is measured and why, and set realistic targets. Bonuses for lower fuel consumption deliver more lasting results than penalties.
- Lock in a technical routine. Cold tire pressure checked monthly, air filters replaced on schedule, services planned via mileage-based alerts, deflectors adjusted to the height of the semi-trailer.
- Optimize routes and refueling. Re-evaluate recurring routes, eliminate the deviations you've identified and plan refueling at the stations with the best price per liter along the route.
- Set up alerts, not reports read once a month. Alerts for sudden level drops, idling above a threshold, speeding and leaving a geographic zone. Reacting the same day is worth far more than a report analyzed four weeks later.
- Re-evaluate quarterly. Compare equivalent periods and check whether the vehicles with the highest fuel consumption have a technical or a behavioral cause.
How to check whether your fuel savings are real
The most common mistake is to compare the current month with the previous month and draw a conclusion. Fuel consumption depends on the season, routes, load factor and the vehicles actually in service, so a superficial comparison can show “savings” that don't exist or hide real ones.
To know what you have actually achieved, measure it like this:
- Use liters per 100 km, not liters per month. Total consumption automatically drops if you drove less; the right indicator is specific consumption, per vehicle.
- Compare equivalent periods. In winter, fuel consumption rises compared with summer, because of heating and higher rolling resistance. Compare the same month in different years or periods with similar conditions.
- Normalize by trip type. Separate urban trips from highway trips, and loaded trips from empty ones.
- Check by vehicle and by driver, not just by fleet. The fleet average hides the extremes: a single vehicle with a technical problem can cancel out the savings achieved across the rest of the fleet.
- Reconcile refueling with the tank level. Every month, compare the liters on receipts and fuel cards with the level increases recorded by the fuel level sensor. Consistent discrepancies indicate either incorrect calibration or a real loss.
- Track leading indicators. Idling hours, harsh braking and the EcoDrive score respond faster than average consumption and show you within the first week whether the measures are taking hold.
If you want a savings figure for your own fleet, the only accurate one is the figure obtained from this kind of comparison on your own data. The general percentages circulating in the market are, at best, rough estimates: the result depends on the type of vehicles, the routes and how undisciplined things were before measurement began.
CargoTrack's solutions for fuel consumption monitoring
CargoTrack GPS monitoring equipment gives you a very clear view of fuel consumption.
The reports provided by our equipment let you apply all the solutions presented above.
The methods for monitoring fuel consumption are:
- GPS Fleet Tracking – which keeps you informed in real time about how the vehicles in your fleet are refueled, the fuel level in the tank, the recorded consumption, the driver's driving style, etc.
- Fuel level sensor (probe)
- Real-time fuel consumption view
- Fuel tank report
- EcoDrive Module
The CargoTrack fuel consumption monitoring solution guarantees 99% accuracy when monitoring fuel with fuel level sensor. Fuel level sensors measure the fuel over the entire height of the tank, which helps avoid blind spots.
The CargoTrack fuel consumption monitoring solution lets you track changes in the fuel level and is the right equipment to cut your fuel costs.
More than 40 modules and accessories can be chosen together with the GPS unit, depending on the type of fleet, and consulting on the right configuration is free. You can see the available options in the GPS monitoring 2026 package, or you can write to us directly via the contact form.
The smallest details can contribute to fuel savings that become significant when calculated across the fleet. Over a year of operation, these savings can make the difference between profit and loss.
Fuel Consumption – Frequently Asked Questions
1. Why does it matter to know how much fuel you use?
Simply put, if you don't know how much you use, you can't control your expenses. By monitoring consumption, you catch potential problems early – whether it's leaks, diesel theft or simply a driving style that empties your tank faster than it should. Bonus: you optimize routes and save money at the pump.
2. How do I actually track consumption — what fuel consumption monitoring options do I have?
You have several options: GPS devices with a fuel level sensor, systems integrated directly into the dashboard, mobile apps or electronic refueling logs. Each one shows you, in more or less detail, how many liters you actually use on each trip.
3. What is the difference between a fuel level sensor, CAN bus data and a flow meter?
The fuel level sensor measures the actual level in the tank, so it shows refueling and suspicious fuel drops. CAN bus data captures the consumption calculated by the vehicle, along with engine speed, idling and driving style, but does not detect theft from the tank. The flow meter measures the fuel that actually reaches the engine and is useful for machinery and generator sets. The most complete picture comes from combining the fuel level sensor with CAN data.
4. Do phone apps work well for fuel consumption monitoring?
They work, but with one caveat: most apps rely on what you enter manually or on the phone's GPS. For an accurate picture, especially if you have a fleet or want technical details, a professional system connected directly to the vehicle is a safer bet.
5. Does GPS really help me reduce fuel consumption?
Absolutely. A modern GPS system doesn't just show you where you're going, it also records how you drive: speed, RPM, braking, acceleration. By analyzing the data, you see exactly where you're “throwing” fuel out the window and what you need to adjust in your driving.
6. What are the main factors that increase fuel consumption?
Aggressive driving, prolonged idling, low tire pressure, aerodynamics spoiled by poorly adjusted deflectors or open windows on the highway, unnecessary weight, inefficient routes and deferred maintenance. There is rarely a single cause; usually several add up.
7. How long does it take to see savings after installing the system?
The first indicators to respond are idling hours and the number of aggressive driving events, visible within the first week. Average consumption per 100 km takes longer, because it depends on routes and the season. A fair assessment is made after at least one month of data, compared with the baseline period before installation.
8. Is the onboard computer enough for fuel consumption monitoring?
For instant consumption, average and range, yes – the onboard computer is useful. But if you want detailed reports, comparisons or automatic alerts, it is worth pairing it with a more comprehensive GPS monitoring system.
9. Does it also work for an entire fleet of vehicles?
It's perfect for fleets. Telematics systems show you the consumption of each vehicle separately, compare performance across vehicles and reveal the drivers or routes with unjustifiably high consumption.
10. How does knowing how I or my drivers drive help me?
It shows you the plain truth: when you accelerate hard, brake often or drive too fast, you use much more fuel. By adjusting driving style based on concrete data rather than impressions, you visibly reduce consumption.
11. Can I catch fuel theft or leaks?
Yes. Modern systems compare how much you put in with how much you actually use and alert you when suspiciously large discrepancies appear. That way, you catch both technical leaks and deliberate theft in time.
12. How do I check whether the savings achieved are real?
Compare consumption in liters per 100 km, not the monthly total, between periods that are equivalent in terms of season and trip type, calculated for each vehicle separately. At the same time, reconcile the liters on receipts with the level increases recorded in the tank. Only then can you separate real savings from a simple drop in mileage.
13. Is it legal to monitor fuel consumption and driver behavior?
Yes, as long as data protection legislation is complied with. Monitoring company vehicles is permitted for legitimate purposes, such as cost control and transport safety, but drivers must be informed in writing what data is collected, for what purpose and how long it is kept, and processing must be limited to work-related activity.
14. Is a fuel consumption monitoring system like this worth the investment?
In most cases, yes. The savings you make by cutting waste and optimizing consumption pay back the investment fairly quickly. Plus, you are always in control of your budget and vehicle performance.
15. How can you tell if a vehicle is using more fuel than it should?
The easiest way is to check whether the vehicle uses more than it should according to the manufacturer's specifications or more than it used to. If you see fuel usage rising steadily even though you drive the same routes and drive the same way as before, something is clearly wrong: the air filters may be clogged, the tires underinflated, or someone may be a bit heavy on the pedal. If you have a modern GPS system installed, you have the advantage of seeing instantly when and where more fuel is being used – and you can fix the problem before it empties your wallet.
