Fuel is usually a fleet's largest variable cost and the easiest to lose. Almost every platform offers “fuel control”, but what gets measured and how changes completely what you can claim afterwards.
The three ways to measure
Capacitive probe in the tank
A tube installed inside the tank that measures level through capacitance variation. It is the most used option in heavy fleets because it measures directly what is inside, regardless of what the engine says.
- Detects well: refills, drains, real level at any moment.
- Detects poorly: instant consumption; the reading swings with movement.
- Requires: opening the tank and calibrating per vehicle.
Reading the CAN bus
The vehicle itself publishes tank level and accumulated consumption on its data bus. Nothing has to be drilled: you read what the vehicle's computer already calculates.
- Detects well: real engine consumption, engine load, idling, exact mileage.
- Detects poorly: drains; many vehicles report level in coarse steps, fine for the dashboard but not for auditing.
- Requires: the model to be supported and sometimes an adapter.
In-line flow meter
Installed in the supply line, it measures the fuel that actually reaches the engine. It is the most precise method for consumption.
- Detects well: consumption with high precision, even at low load.
- Detects poorly: what happens in the tank; siphoning never passes through the line.
- Requires: intervening in the fuel circuit, with everything that implies for warranty and maintenance.
Which to choose
| If you want to… | Use | Why |
|---|---|---|
| Detect fuel theft | Probe | It is the only thing that sees the tank directly |
| Measure driving efficiency | CAN | It links consumption to engine load and style |
| Audit consumption precisely | Flow meter | It measures the real flow to the engine |
| The most complete picture | Probe + CAN | Tank and engine tell different stories |
The step almost nobody gets right: calibration
This is where most implementations stop being useful. A tank is not a perfect cylinder: it has an irregular shape, it sits at an angle and the probe does not respond linearly across its whole range. If you take the raw reading and convert it to litres with a simple ratio, the result will not survive an argument with the customer.
A bad calibration does not produce a constant error: it produces an error that changes with how full the tank is. That is the worst kind, because it looks random.
How to calibrate properly
- Empty the tank as far as is safe and record the probe reading.
- Add known volume in increments, for example twenty litres at a time.
- Record the reading at each increment, with the vehicle level.
- Repeat until full. You will end up with fifteen to twenty points.
- Load that table into the platform as the vehicle's curve, not as a formula.
It is an hour of work per vehicle and it has to be repeated if the probe is replaced or the tank is opened. It is tedious, and it is exactly the difference between a report that serves as evidence and one the customer dismisses.
Filtering: why the level “jumps”
A tank in motion sloshes. A corner, a braking event or a slope move the fuel and the probe reports it as a level change. Without filtering, the system sees drains where there was only a roundabout.
Good filtering combines several things: a moving average over a time window, discarding readings while the vehicle is tilted or accelerating, and confirming that a drop is sustained before declaring it a drain. If your platform raises siphoning alerts every day, the problem is probably not the drivers.
Reconciling with the receipt
Refill detection has an underrated value: cross-checking it with the station receipt. The system records that the tank took a hundred and twenty litres at 14:32 at a given coordinate; the invoice says a hundred and fifty. That difference, repeated, is a pattern.
What to ask of the platform
- A calibration table per vehicle, not a single factor
- Configurable filtering, with the parameters visible
- Refill and drain detection with volume, time and coordinate
- Automatic correlation between level drop and engine load
- Reconciliation with receipts or with the supplier invoice
- Efficiency reporting by route and by driver, not only by vehicle
To close
Fuel control does not fail for lack of sensors: it fails through rushed calibration and absent filtering. A cheap device calibrated well gives better results than an expensive one installed in a hurry.
