What is fuel card leakage?
Fuel card leakage is fuel paid for on fleet fuel cards that you cannot match to fuel your vehicles used. Part of it usually has an ordinary cause: idling that the consumption figure leaves out, fuel still in the tanks at the end of the period, pump and odometer measurement error, rounding on receipts, or a card used for a generator or other equipment. Part of it may be misuse. This calculator measures the gap; it does not tell you why the gap exists.
The first tab compares the liters on your card statements with the liters the fleet should have used, from distance and consumption or from telematics fuel data, and turns the difference into a value per period and per year. The second tab checks individual fill-ups against rules you set and flags the ones worth a second look.
Why unexplained fuel matters
- Fuel is a large running cost. A small share of unexplained liters across a whole fleet adds up over a year.
- Card statements show spend, not use. They tell you what was bought and where, not whether the vehicle burned it.
- Small patterns hide in totals. Fills larger than the tank or two fills an hour apart do not stand out on a monthly invoice.
- Consistent rules are fairer. Checking every fill against the same rules is more defensible than reacting to one suspicion.
What you need to check fuel card purchases
| Input | Where to find it | Tip |
|---|---|---|
| Liters bought | Fuel card statements | Use the statement period that matches your distance figures. |
| Distance driven | Odometer readings, trip reports or telematics | Take readings on the same dates as the statement period. |
| Expected consumption | Your own fuel log, by vehicle type | Use the figure for real duty (load, traffic, air conditioning), not the brochure figure. |
| Fuel used | Telematics with CAN bus or fuel sensor data | Choose the telematics method to skip the consumption estimate. |
| Fill-up details | Card transaction export: vehicle, date, time, liters, odometer | Ask drivers to enter the odometer at every fill. |
| Tank capacity | Vehicle specification or registration documents | Use the usable capacity where you know it. |
How to calculate unexplained fuel
Fleet level
The tolerance covers normal differences from measurement and rounding. Set it before you look at the result and keep it the same each month.
Fill-up checks
Fills are grouped by vehicle name and put in date and time order before the sequence checks run. If shifts run overnight, enter an end hour earlier than the start hour. The consumption column assumes each fill tops up the tank.
Worked example: fuel card reconciliation
A fleet bought 12,500 L on its fuel cards in one month and drove 38,000 km at an expected 30 L/100 km.
- Driving fuel is 38,000 × 30 ÷ 100 = 11,400 L. With 300 L of idling, expected use is 11,700 L.
- The gap is 12,500 − 11,700 = 800 L, or 6.4% of liters bought.
- A 3% tolerance is 375 L, which leaves 425 L unexplained: 3.4% of liters bought and of fuel spend.
- At a fuel price of 1.10 per liter, that is 467.50 for the month, or about 5,610 a year if the pattern holds.
- The fill-up tab checks eight fills with working hours of 06:00 to 20:00, at least 4 hours and 150 km between fills, and a 5% allowance above tank capacity. Five fills are flagged: a second fill of Van 01 2.6 hours and 80 km after the first, Truck 02 at 23:10, 230 L into Truck 02's 200 L tank, a Pickup 03 fill with no odometer reading, and Van 04 at 05:20. They hold 570 L of the 746 L bought.
How to read your fuel card results
- Unexplained fuel above zero is a reason to look closer, starting with the vehicles and cards with the largest purchases compared with their distance.
- A gap within the tolerance means your purchases match your consumption figures as closely as your data allows.
- Purchases below expected use usually mean fuel from another source, such as a depot tank or cash purchases, or a consumption figure set too high.
- Each fill-up flag is a question for the receipt, the trip record and the driver, not a finding. Record the explanation either way.
Common mistakes when reconciling fuel cards
- Mismatched periods. A statement from the 1st to the 30th compared with odometer readings taken on other dates creates a gap that is not real.
- Using the brochure consumption. Manufacturer figures are usually lower than real duty, which makes normal use look unexplained.
- Leaving out idling and tank levels. Fuel burned while parked and fuel still in the tank both count as purchases with no distance behind them.
- Treating a flag as proof. Late shifts, a top-up before a long trip, a typing error or a wrong tank figure all produce flags.
- Moving the tolerance after seeing the result. Agree it with finance first and keep it stable so months can be compared.
Assumptions and limits
Results are estimates based on the values entered. Real consumption changes with load, traffic, terrain, air conditioning and driving style, so the fleet-level gap is only as good as the consumption figure behind it. The fill-up checks use the tank capacity, hours and limits you enter; they do not check days off, locations or which card was used on which vehicle. Times are read as entered, so make sure the card export and your working hours use the same time zone. Nothing here is legal or HR advice: follow your company policy and look at the evidence before taking any step with a driver.