What is wetstock management?
Fuel goes missing for six different reasons, and five of them are harmless. Guess wrong and you either dig up a forecourt or ignore a leak.
Wetstock management
wetstock analysisfuel inventory management
Wetstock management is the practice of tracking liquid fuel from delivery through storage to sale. Its job is to explain any gap between the fuel a site should hold and the fuel it measures, so a real loss can be told apart from a measurement error before anyone acts on it.
Three numbers meet at every tank. What was delivered, what was sold, and what the gauge says is left. Subtract and you get a figure the industry calls variance. It is almost never zero.
Wetstock is the fuel itself. Managing it means watching those three numbers over weeks rather than days, because the causes of variance only separate over a statistical window. One day of data tells you nothing you can act on.
Six causes look identical in a daily number
Fuel expands and contracts with temperature, so a cold delivery into a warm tank changes the volume without changing the molecules. Meters drift with use. A short load arrives and nobody catches it at the rack. Water gets in at the fill point. Someone takes product. And a tank or a line leaks.
Each of those produces the same symptom on a report: gallons that are not there. Sites respond in one of two wrong ways. They ignore the number, which is how a real release gets missed. Or they investigate every wobble, which sends technicians to sites where nothing is wrong until nobody believes the system.
The pattern is what tells them apart. A leak trends one way and does not stop. Temperature effects follow the season and the time of day. A drifting meter shows up on one dispenser and not its neighbour.
- 01Temperature change, which alters volume without altering quantity.
- 02Meter drift on a dispenser or a truck meter.
- 03Short deliveries, disputed at the rack days after the fact.
- 04Water at the bottom of the tank, which the gauge reads as product depth.
- 05Theft.
- 06A genuine release from the tank or the piping.
- DeliverBill of lading, gross or net.
- StoreGauge reads depth, not volume.
- ConvertTank chart turns depth into gallons.
- SellDispenser meters count out.
- CompareBook against measured.
- ExplainPattern over weeks, not days.
The third step is where accuracy is quietly won or lost. If the tank chart is slightly wrong, every reading is slightly wrong, and the error changes as the tank empties.
Related questions
01How is wetstock management different from leak detection?
Wetstock management is the broader practice of accounting for fuel and explaining variance from any cause. Leak detection is one regulated conclusion you can draw from it, and the methods that qualify have to meet published performance standards. Software that analyses wetstock is not automatically a certified detection method.
02Can AI do wetstock analysis?
Separating causes of variance is a genuine statistical problem, so this is one of the honest analytics cases in fuel. What it is not is a language model job. The work is regression, seasonality and change detection over a window, plus a data model that never mixes volume bases.
03How much variance is normal?
There is no single figure, because it depends on the tank, the equipment and the accuracy of the tank chart. That is why the useful question is not how big today's number is but whether it trends. A small steady loss matters more than a large one that reverses next week.
04Why does water at the bottom of the tank matter?
Water sits under the fuel and a level probe reading depth can count it as product, so the tank looks fuller than it is. It also signals a way in for water, which points at tank or fill-point integrity, and it feeds microbial growth in diesel. Gauges measure two levels for this reason.
Related reading
- Statistical inventory reconciliation →The regulated method that turns wetstock data into a leak conclusion.
- Reconciliation →The same idea applied to money: two records, and every difference explained.
- Energy and fuel software development →What we build for fuel distributors and site operators.
- TankAware →Petroleum site management for Sutherland Excavating Ltd.
