Fuel is one of the largest operating costs a fleet carries. For heavy vehicle and trucking operations, diesel is commonly cited at around 30 to 40 per cent of total running costs; for light vehicle fleets the share is smaller but still material. Either way, tracking usage per vehicle is what turns fuel from an unexamined bulk expense into something you can question, benchmark and control.
This guide covers the full process, from recording fill-ups to calculating consumption, comparing against sensible reference ranges, and acting on anomalies. It also covers why clean fuel records matter at tax time in Australia.
Before you start
Download a fuel usage log sheet to standardise how your team records data. You will also need odometer readings for every vehicle and either fuel receipts or bowser data from your supplier. If you run fuel cards, export the transaction history so you can reconcile it against logged fill-ups later.
Step-by-step fuel tracking
1. Record the starting odometer and fuel level
Use the full-tank method for accuracy. Fill the tank completely, then note the odometer reading. This becomes your baseline for the next measurement period.
2. Fill the tank and capture the reading
At the next fill-up, record four data points: litres added, total cost, date and the driver's name. Fill the tank completely again so the odometer difference represents the exact distance driven on the fuel consumed.
3. Calculate consumption
(Litres used / kilometres driven) x 100 = L/100km
For example, 65 litres over 720 km gives (65 / 720) x 100 = 9.03 L/100km. Record this alongside the raw data so you can trend it over time rather than reading a single tank in isolation.
4. Log the entry
Each entry should include date, vehicle ID, driver, odometer, litres, cost and the calculated L/100km. Pair the fuel log with a vehicle mileage log so distance and consumption reconcile against each other.
5. Compare against the vehicle's own baseline
The most reliable benchmark is the same vehicle's own history under similar conditions, followed by the OEM specification and the average for that vehicle type in your fleet. A vehicle sitting consistently above its established baseline, or above comparable units doing the same work, is the one worth investigating.
6. Review and act on anomalies
A sustained rise of more than roughly 15 per cent above a vehicle's own baseline is worth investigating. Work through the common causes table below before booking it in with a mechanic, and flag the vehicle for service if no operational reason explains the increase.
Indicative consumption ranges
The ranges below are indicative starting points for a sanity check, not published averages. Real consumption depends heavily on load, terrain, body type and duty cycle, so build your own baselines from your logged data and treat these only as a rough guide.
| Vehicle type | Indicative L/100km | Worth a look above |
|---|---|---|
| Light vehicle (sedan/ute) | 8 to 12 | 15 |
| SUV / 4WD | 12 to 16 | 20 |
| Light truck (up to 4.5t) | 15 to 25 | 30 |
| Heavy truck (rigid) | 25 to 40 | 48 |
| Heavy truck (articulated) | 35 to 55 | 65 |
| Van / minibus | 10 to 15 | 18 |
Common causes of high fuel use
When consumption climbs above the vehicle's baseline, work through these causes before escalating to a mechanic.
| Cause | What to check |
|---|---|
| Underinflated tyres | Check all tyres against placard pressure |
| Excessive idling | Review idle time via GPS tracking |
| Poor route planning | Compare planned against actual routes for detours |
| Overloading | Verify payload against the GVM rating |
| Aggressive driving | Check harsh braking, rapid acceleration and speeding |
| Missed maintenance | Inspect air filter, spark plugs and fuel injectors |
| Fuel theft or misuse | Reconcile fuel card transactions against logged fill-ups |
| Incorrect tyre size | Confirm fitted tyres match the OEM specification |
Manual vs automated tracking
Many fleets start with spreadsheets and move to software as the fleet grows and manual collation stops keeping up.
| Factor | Manual (spreadsheet) | Automated (software) |
|---|---|---|
| Data entry | Paper form or spreadsheet | Mobile app or fuel card integration |
| Accuracy | Prone to transcription errors | Validated at entry with GPS confirmation |
| Time cost | High, manual collation required | Low, automatic calculations and reports |
| Reporting | Basic spreadsheet charts | Dashboards with anomaly alerts |
| Maintenance link | None, separate notification needed | Anomalies can trigger a service booking |
Fuel records and fuel tax credits
In Australia, accurate per-vehicle fuel records do more than expose waste, they underpin fuel tax credit claims. Businesses can claim credits from the ATO for the fuel tax already included in the price of diesel used in their vehicles and machinery, and the rate differs for fuel used on public roads compared with fuel used off-road or to run auxiliary equipment, because a road user charge reduces the on-road credit. Whatever you claim has to be substantiated by records, so a clean fuel log is worth money at tax time, not just for spotting the thirsty vehicle in the yard.
Whichever method you use, the payoff is the same: fuel data is only useful when it is trended per vehicle and cross-checked against idle time and route data so you can tell a hard duty cycle from a genuine fault. Poorly maintained vehicles are consistently the worst performers, and catching a blocked air filter early often pays for itself within a single tank.
