Ask three people in a transport operation what a vehicle costs to run and you will get three numbers. The fleet manager quotes fuel. Finance quotes fuel plus the workshop invoices they can find. The owner quotes something closer to the truth and cannot show the working.
Cost per kilometre is a simple formula sitting on top of data that is usually a mess. The formula is not the hard part.
What belongs in the number
A defensible cost per kilometre has four components. Leave any of them out and you are comparing vehicles on an incomplete basis.
- Fuel
- Issued against the vehicle, not the driver. This single distinction is why many fleets cannot calculate consumption at all.
- Maintenance
- Parts, labour and external workshop bills, attached to the vehicle through a job card rather than posted to a general repairs account.
- Tyres and consumables
- Tracked by position and life, not expensed in the month of purchase. A tyre bought in March and worn out in November belongs across both.
- Fixed costs
- Registration, fitness, insurance, token tax and depreciation, apportioned across the distance actually run.
The denominator is where it breaks
Distance sounds trivial and rarely is. Odometer readings captured by hand drift, get transposed, or are entered at the end of the week from memory. One mistyped reading can make a vehicle look twice as efficient as it is for a whole month.
Capture the odometer at the gate, on both the outward and return legs, and have the system reject a reading lower than the last one. That one validation removes most of the noise.
If you run GPS, reconcile it against the odometer rather than replacing it. GPS distance and odometer distance disagree for legitimate reasons, and a persistent gap on one vehicle is itself a useful signal.
Why downtime belongs in the calculation
A vehicle sitting in the workshop still accrues fixed cost and covers no distance. If downtime is not recorded, that cost silently spreads across the vehicles that were working, which flatters the broken one and penalises the rest.
This is the practical reason fleet and workshop systems should share a vehicle master. When a job card opens, the unit becomes unavailable for allocation and its off-road time is recorded. The cost per kilometre then reflects reality without anyone reconciling two systems.
Reading the result
Once the figure is trustworthy, three comparisons earn their keep.
Against the fleet average for the same category — comparing a prime mover with a pickup tells you nothing. Against the vehicle's own history, where a steady climb usually arrives before a major failure. And against replacement cost, which is the comparison that actually drives a decision: at some point the annual running cost of an old unit exceeds the financing cost of a new one, and the number tells you when.
What good looks like
You should be able to answer, without preparing anything: what did this vehicle cost per kilometre last month, how does that compare with its category, how many days was it off road and why, and which documents expire in the next sixty days.
If producing those answers takes a spreadsheet and an afternoon, the data exists but the system does not.
Common questions
Should depreciation be included in cost per kilometre?
For a replace-or-keep decision, yes — it is a real cost of operating the asset. For comparing driver or route efficiency, exclude it, since it has nothing to do with how the vehicle is being used. Report both and label them clearly.
How do we handle fuel issued to a driver rather than a vehicle?
Change the process. Fuel logged against a driver cannot produce a per-vehicle consumption figure, and no amount of reporting will reconstruct it afterwards. Issue against the vehicle and record the driver separately.
Is GPS distance better than the odometer?
Neither is authoritative alone. Use the odometer as the book figure and GPS as the check. A consistent gap on one vehicle is worth investigating rather than averaging away.