The Overnight Loss Ledger: Justifying Anti-Theft Spend on a UK Van Fleet

Overnight fuel loss rarely announces itself. A van returns full and leaves with less; no warning light, no dramatic incident. For UK operators, the temptation is either to ignore it or to buy security by habit. A disciplined audit does something more useful: it separates the routes by which fuel leaves the tank, attaches a realistic cost to each, and tests the defence against that cost. The aim is not a fortress. It is a defensible line in the fleet budget.

Begin with the reconciliation, not the lock

Before buying anything, establish a baseline. For each van, compare fuel purchased — from fuel-card statements or bunker drawdown — with miles travelled and a realistic MPG band. In 2026, a Ford Transit Custom on mixed urban work may return low 30s mpg; a heavier panel van will be lower. The point is variance, not absolute accuracy. If one van consistently consumes 8–12% more than its stablemates on similar duty, it deserves a second look. That look should cover driver behaviour, maintenance, and only then theft. A weekly reconciliation, run by one person and reviewed monthly, is the cheapest control in the programme.

Three exits from the tank

Fuel leaves a van by three broad routes, and each leaves a different trace.

Physical extraction — siphoning or pumping from the filler neck — usually produces a sudden drop while the vehicle is stationary and the ignition is off. Modern vans have anti-siphon devices, but they are not universal and can be defeated. The tell is a fuel-level fall that is not matched by mileage, often over a weekend or a bank holiday.

Tank penetration — drilling or puncturing the tank — is cruder and more expensive. It tends to happen in unlit yards or on-street parking. The signature is a larger, one-off loss, often accompanied by a visible stain or a strong smell. Repair costs can exceed the fuel lost, so the case for prevention here is about downtime as much as diesel.

Card and process misuse — the card is part of the tank. After-hours fills, repeated small purchases, fills that exceed the tank capacity, or transactions far from the vehicle's geofenced area all point to a control weakness. So does a mismatch between the odometer reading at the pump and the telematics record.

Telematics signatures worth paying for

Not every telematics feature earns its subscription. For overnight loss, four are relevant. First, fuel-drop detection: an alert when the level falls by more than a set percentage while the ignition is off. Second, geofence alerts for after-hours movement or card use outside expected areas. Third, ignition-state reporting, which distinguishes a parked vehicle from one idling in a yard. Fourth, odometer capture at fuelling, ideally automatic. The quality of the fuel-level sensor matters; a float sensor that moves with cornering will generate false alarms. Set thresholds with the supplier, review the first month's alerts, and adjust. An alert that cries wolf every night will be ignored within a fortnight.

What the losses actually look like

A realistic model for a 40-van UK fleet is more modest than headline figures suggest. Assume diesel at £1.50 per litre. A single siphoning incident might remove 40–60 litres, or £60–£90. If the fleet suffers one such incident per van per year — a high rate for most depots — the annual loss is £2,400–£3,600. Add tank-penetration repairs at £400–£700 per event, and a handful of card irregularities, and a plausible annual exposure sits between £4,000 and £6,000. That is not a trivial sum, but it is not a reason to buy every device on the market either.

Costing the defences

Locking fuel caps: £40–£80 per van, or £1,600–£3,200 for 40 vans. They raise the effort required and deter opportunistic theft; they do not stop a determined attack. Park positioning: nose-in against a wall or in a well-lit, camera-covered area costs little beyond layout discipline. Fuel-drop alerts: often a configuration item on an existing telematics contract, but if it requires a sensor upgrade, budget £150–£300 per van. Reconciliation labour: two hours a week at £30 per hour is £3,120 a year, though much of it can be absorbed into existing admin. A sensible package — caps, positioning, alerts on the highest-risk vans, and weekly reconciliation — can be delivered for £3,000–£6,000 in year one, with lower ongoing costs.

A 30-day trial before a fleet-wide roll-out

Rather than fit every van at once, run a trial on the ten vehicles with the highest unexplained variance or the least secure parking. Fit locking caps, configure drop alerts, and move those vans to the best available bays. Reconcile weekly and record every alert and its outcome. At the end of the month, compare losses and admin time against the baseline. If the trial shows no measurable reduction, the case for extending the spend is weak. If it does, the numbers are already in the budget format a finance director will recognise.

The decision rule

Spend should follow evidence, not habit. If the reconciliation shows no unexplained variance across a quarter, a fleet-wide locking-cap programme is hard to justify. If two vans account for most of the variance, target those vans and the parking bays they use. If card irregularities dominate, the answer is process and exception reporting, not hardware. The audit does not need to be complex. It needs to be repeated, recorded, and connected to the budget line it protects.

The night shift will always be less visible than the day. The ledger makes it visible enough to manage.