Most fleet managers know they're losing fuel. The signals are obvious — fuel costs creeping up without a corresponding increase in distance, drivers buying suspiciously low quantities at suspicious stations, the same vehicle averaging two very different consumption rates depending on the driver.
But knowing fuel is being stolen and proving it are two different things. And until you can prove it, you can't act.
The three patterns of fleet fuel theft
In our experience deploying FuelPortal across 80+ South African fleets, fuel theft falls into three patterns:
1. Mid-route siphoning. The classic. Driver stops in a quiet area, siphons 30–80 litres into a jerry can, sells it. Hard to detect with fuel-card data alone because the tank fill is legitimate — it's the drain hours later that matters.
2. Inflated receipts. Driver fills 200 litres but the receipt reads 250 litres. The forecourt attendant gets a cut. Without verified tank-level monitoring, the difference is invisible.
3. Card sharing. Driver uses the company fuel card to fill personal vehicles or family vehicles. Often combined with kickbacks at preferred stations.
What detection actually requires
You need three data points working together:
- Real fuel level, sampled at high frequency, from a calibrated tank sensor — not the OEM gauge.
- Calculated consumption, derived from CANbus distance and engine hours.
- GPS position, to correlate level changes with location.
When all three agree, fuel use is normal. When the level drops faster than calculated consumption predicts — at a specific GPS location — you've found a drain event.
That's the entire mechanic. FuelPortal automates it across the fleet, flags discrepancies, and produces a per-driver theft report at month-end.
What it doesn't catch (be honest)
Drivers occasionally swap fuel between tanks, run engines unnecessarily to mask theft as 'idle consumption', or work in pairs to fake fills. No system is perfect. The point is to make the theft expensive — in time, coordination, and risk — relative to its reward. Most operators see a 20–30% drop in unexplained fuel consumption in the first 90 days.
That's not theft eliminated. That's theft becoming uneconomic.