Diesel is usually stolen in a few ways: siphoned or drained from the tank while a vehicle or generator is parked, claimed through refuels that never reached the tank (inflated receipts and ghost refuels), taken with a misused fuel card, or removed from storage tanks and depots. A capacitive fuel-level sensor that reads the tank in litres, cross-checked with GPS position and engine state, shows when and where the litres disappeared. It does not say who took the fuel, but it tells you exactly what to check.
How diesel theft happens
Operators across DRC describe the same handful of methods. Each relies on the gap between the fuel paid for and the fuel anyone measured.
- Siphoning from the tank. A hose through the filler neck into jerrycans, usually at night or in an unguarded yard.
- Draining through the drain plug or fuel line. Fuel let out through the tank’s drain plug or a loosened fuel line, then blamed on a leak.
- Ghost refuels and inflated receipts. A receipt for more litres than went into the tank, or for a refuel that never happened.
- Fuel card misuse. A company card used to fill another vehicle, a private car or jerrycans.
- Generator sites and storage tanks. Remote tanks are rarely visited; fuel removed between deliveries is recorded as burned.
- Collusion at depots. When the person who dispenses fuel and the person who records it work together, the paperwork balances while the tank does not.
- Long-haul trips. Operators running trucks toward Matadi on the N1, or along the mining corridors of Haut-Katanga and Lualaba, describe fuel sold during long stops and later explained as heavy consumption on bad roads.
Warning signs you can check without sensors
Your own records already show where to look. Check these each week, per vehicle and per generator:
- Consumption per kilometre is rising. Compare litres per 100 km for the same vehicle and route over several weeks. A step up with no change in load or driver deserves a question.
- A refuel larger than the space in the tank. If a receipt shows more litres than the tank could take, part of that fuel went elsewhere.
- Refuels away from the route. A station the vehicle had no reason to visit, or a time it should have been parked. With GPS tracking, compare the receipt time with the vehicle’s position.
- Engine hours that do not match kilometres. Many engine hours with few kilometres can mean long idling, or records adjusted to explain the fuel used.
- Generators burning more per hour than they should. Divide the litres delivered by the hours run and compare the result with the manufacturer’s consumption figure for that load.
These checks find patterns, not proof, and they rely on receipts and logbooks that can themselves be wrong.
What a fuel sensor sees
A capacitive fuel-level sensor sits inside the tank and measures the level continuously; a calibration table built for that tank turns each reading into litres. Combined with GPS position and ignition state, every change in the tank gets a time, a place and a context.
In plain words: a sudden drop while the vehicle is stopped with the ignition off is the typical sign of a drain or siphon, because a stopped engine burns no fuel. A refuel shows as a quick rise; its size is the volume that actually entered the tank, to set against the receipt. A slow, steady decline at rest points to seepage from a leak. Sloshing on slopes and rough roads makes the reading swing and come back, which is why events need validation: a drop only counts once the level is stable.
The fuel monitoring guide covers the procedure: tank inspection, calibration and event validation.
| Pattern | What it usually means | What to check |
|---|---|---|
| Fast drop while stopped, ignition off | Fuel drained or siphoned | Position on the map, time, who had the vehicle, cap and drain plug |
| Refuel rise smaller than the receipt | Inflated receipt, or part of the fuel went into jerrycans | Receipt, station, card transaction, time spent at the station |
| Receipt with no rise in the tank | Ghost refuel | GPS position at the time on the receipt, card statement |
| Drop while driving, faster than normal consumption | Leak, or fuel taken from the line | Fuel lines, tank fittings, consumption per kilometre |
| Slow decline over hours, engine off | Leak, or small repeated removals | Tank and fittings; the same hours on other nights |
| Generator fuel level falls while the generator is stopped | Fuel removed at the site | Runtime hours, site access, delivery records |
How GT AFRIK detects it
GT AFRIK measures the tank with capacitive fuel-level sensors. Escort and Omnicomm sensors are integrated. The featured sensor is the Escort TD-BLE, which gives readings in litres with ±1% volume accuracy and pairs wirelessly over Bluetooth Low Energy with Teltonika FMB920 and FMB125 trackers. Escort documents a measurement error of no more than 1% [1] and lists both trackers as compatible [2].
Each reading is cross-checked against GPS position and engine (ignition) state, and a suspicious drop triggers a WhatsApp alert in about 60 seconds. On the platform you see:
- a fuel chart: the tank level over time, with refuel and drop events marked;
- fill and eject reports, listing each refuel and each removal;
- fuel consumption reports;
- theft and drain reports.
For generators, a Teltonika FMB125 reads DSE, ComAp and DATAKOM controllers over Modbus RTU and reports runtime hours, fuel level, battery voltage and alarms (see generator monitoring). Setting fuel level against runtime hours shows whether the generator burned the fuel or it left the tank another way.
GT AFRIK is headquartered in Kinshasa, with local teams in Kinshasa, Lubumbashi and Brazzaville. Its own technicians install the equipment, systems are typically live within 48 hours and no long-term contract is required. Dashboards, reports and support are available in French and English. See the fuel monitoring service, the supported devices and GPS tracking in Kinshasa.
A 7-step response plan when an alert fires
- Verify the event on the chart. Check that the level fell and stayed down once the reading was stable, rather than swinging back.
- Check the GPS location and time. Depot, station, roadside stop, or somewhere the vehicle had no reason to be?
- Check the ignition state. A drop with the engine off is not consumption. A drop while driving points more toward a leak or a fuel-line problem.
- Call the driver or the site. Ask what happened there before saying what the data shows.
- Inspect the tank and seals. Cap, lock, seal numbers, drain plug and fuel lines: look for fresh marks or wet fittings.
- Compare with receipts. Set the fill and eject report against receipts and fuel card transactions for the same period.
- Record the outcome and adjust. Note the conclusion (theft, leak, sensor fault or unresolved) and what changes: seals, locking caps, parking rules, card limits.
Keep the record even when an event proves harmless; over months it shows which vehicles, sites and routes need attention.
Prevention measures
Detection shows what happened; these measures make theft harder:
- Locking fuel caps on every vehicle and generator tank, keys held by someone other than the driver.
- Anti-siphon devices in the filler neck, so that a hose cannot reach the fuel.
- Numbered seals on caps, drain plugs and generator tanks, with the numbers recorded at every refuel and inspection.
- Parking in lit, guarded areas, with a rule on overnight stops during long trips.
- Fuel card limits. Tie each card to one vehicle, set limits per refuel and per day, and allow approved stations only.
- A reconciliation routine. Each week, compare receipts, card statements and the sensor’s refuel events; each morning, review the night’s fuel events. The fleet manager’s daily checklist fits this into 15 minutes.
Separate duties where you can: the person who approves fuel should not be the person who reconciles it.