Every transporter has asked the question in some form: "fuel chori kaise pakde?" The usual answer is a fuel level sensor dropped into the tank. It works, but it costs ₹4,000 to ₹9,000 per vehicle plus calibration, it drifts on rough roads, and on a 10-truck fleet it is a ₹70,000 decision. There is a cheaper method that catches most theft, and it needs only two things you already have: the GPS tracker and the fuel bills.
The idea: mileage per stretch
A truck's fuel economy does not change much from week to week on the same kind of route. If it does 4.2 km per litre this month and 3.1 km per litre next month with the same loads and the same roads, 25 percent of the diesel went somewhere other than the engine.
To measure mileage you need two numbers: litres put in, and kilometres run on those litres. The GPS gives the kilometres exactly. The litres come from the pump bill. The only discipline needed is to fill the tank full every time so that each refill starts from the same level.
The full-tank method, step by step
- Fill full, note the litres. At every refill, the driver fills to the auto-cutoff and records litres and amount (from the pump receipt).
- Record the odometer or GPS distance. With a GPS tracker this is automatic: the position and odometer at the time of the bill are already there.
- Wait for the next full fill. The litres of the second fill are exactly what the truck used since the first fill, because both times the tank was full.
- Divide. Kilometres between the two fills ÷ litres of the second fill = km per litre for that stretch.
- Compare. Put each stretch next to the last five. A stretch that is 15 to 20 percent below the average needs an explanation.
Partial fills (₹2,000 of diesel on the way) are fine, as long as they are recorded. They are added to the next full fill's litres; the stretch simply gets longer.
What a fuel theft looks like in the numbers
- Mileage drop on a normal route. The clearest sign. The route, load and driver are the same, but km per litre falls. Diesel is being drawn from the tank, or the pump is short-filling.
- Overfill. A bill for 320 litres on a truck with a 300-litre tank. Either the pump cheated or the driver bought diesel for someone else on the company account.
- Refill while moving. A bill timed when the GPS shows the truck doing 60 km/h on the highway, 30 km from the pump. The receipt is not from this truck.
- Refill location does not match. The bill says a pump in Kanpur, the GPS shows the truck at a dhaba in Unnao at that time.
- Mileage too good. A sudden rise in km per litre can mean the previous fills were not really full, or kilometres are being added. It is worth a look too.
Where the diesel usually goes
Knowing the method helps you ask the right question when a stretch fails:
- Siphoning at night from a parked truck, by the driver or by outsiders. Pairs with parking alerts: a vehicle that is "parked" but shows a power cut or vibration alarm at 2 a.m.
- Short fills at the pump, where the driver and the attendant split the difference between the bill and the actual litres. Shows as a mileage drop only at one particular pump.
- Fuel bought for another vehicle on the company card. Shows as overfill or as a refill far from the truck.
- Excess idling with the AC on. Not theft, but it burns 1 to 2 litres per hour and shows as the same mileage drop. The GPS idle report separates it from theft.
Doing this with SaralTrack
SaralTrack's fuel log is built around this method, so none of the arithmetic is done by hand:
- The driver or manager adds a refill in the app: litres, amount, full or partial, with a photo of the bill. Odometer and location are taken from the GPS at that moment.
- When the next full fill is logged, the stretch closes and the system writes distance, litres used, km per litre and cost per km.
- Each stretch is compared with the average of the previous five. The system flags mileage drop, overfill (above the tank capacity you set) and refill while moving, and sends an alert through the normal channels.
- The fuel report for any period shows expected litres (from the vehicle's rated consumption) against actual litres, per vehicle.
The setup is one field per vehicle: tank capacity. See the fuel log on the features page for a working demo.
When a sensor is still worth it
A fuel sensor shows the level in real time, so it catches a 40-litre drop at 2 a.m. within minutes rather than at the next refill. If you have a few high-value vehicles that park in unsafe places, or you are losing fuel between refills and cannot catch who, add a sensor to those vehicles only. For the rest of the fleet the full-tank method, with a fuel log that does the comparison for you, finds the pattern at almost no cost.
Frequently asked questions
Can I detect fuel theft without a fuel sensor?
Yes. Fill the tank full at every refill, record litres and let the GPS record the kilometres. Kilometres between full fills divided by litres gives mileage per stretch, and stretches well below the average point to theft, short-filling or excess idling.
How accurate is the full-tank method?
Accurate to a few percent as long as fills are genuinely full and recorded. It will not show a 5-litre loss on a single trip, but it reliably shows a 10 to 20 percent pattern over two or three stretches, which is where most theft sits.
What if the driver does not fill full?
A partial fill is recorded as partial and carried into the next full fill. The stretch becomes longer but the mileage figure stays correct. If a "full" fill was actually partial, the next stretch shows an unusually high mileage, which is itself a flag.
Does SaralTrack need any extra hardware for fuel tracking?
No. The fuel log uses the GPS tracker already in the vehicle and refill entries from the app. A fuel level sensor can be added later for vehicles that need real-time level monitoring.