Towing & caravans
Towing does not add a fixed surcharge to a trip — it changes the shape of the fuel curve. This section covers what drives the penalty, why the number people quote is usually too low, and what it costs at today's diesel price.
Tools in this section
- Towing Fuel Cost CalculatorThe difference between the same trip loaded and unloaded — extra litres, extra dollars, and what a 10 km/h speed change does to both.
- Trip Fuel Cost CalculatorEstablish the unloaded baseline for a route first, then apply a towing penalty to it.
- Fuel Budget PlannerSpread a towing season across a year — several trips, mixed loaded and unloaded driving.
Frontal area matters more than mass
The intuition most people bring to towing is that heavier means thirstier. That is true on hills and in stop-start traffic, where you are repeatedly accelerating mass. At a steady 100 km/h on a highway it is largely wrong. At that speed most of the engine’s work goes into pushing air, and aerodynamic drag scales with frontal area, not weight.
This is why a 1,200 kg box trailer sitting low in the tow vehicle’s slipstream can cost you 15% while a 1,200 kg full-height caravan — same mass, roughly three times the frontal area, and tall enough to sit in clean air above the car’s wake — costs 50% or more. If you are choosing between two vans of similar weight, the shorter and narrower one will be materially cheaper to tow.
Typical penalties by trailer type
The figures below are the starting ranges the calculator uses. They are a place to begin, not a substitute for measuring your own combination — the same van behind a dual-cab ute and behind a large SUV can differ by 10 percentage points because of how the air leaves the tow vehicle.
What that costs on a real trip
A 2,000 km round trip — Sydney to Byron and back, roughly — in a tow vehicle that uses 10.5 L/100km unloaded, priced at the five-city average diesel price of 243.9 cpl:
| Configuration | Penalty | Fuel | Cost | Extra vs unloaded |
|---|---|---|---|---|
| Unloaded | — | 210 L | $512 | — |
| Box trailer | +15% | 241 L | $589 | +$77 |
| Boat on trailer | +25% | 263 L | $640 | +$128 |
| Pop-top van | +35% | 284 L | $691 | +$179 |
| Full-height van | +55% | 326 L | $794 | +$282 |
The full-height van adds more to the fuel bill for one trip than most people budget for the whole holiday’s fuel. It is also the number that changes most if diesel moves: every 10 cpl on the pump price adds about $33 to that trip. Diesel has been unusually volatile in 2026 — see the fuel price data page for the excise timeline behind that.
Speed is the lever you actually control
Because the penalty is mostly aerodynamic, it scales with speed in the same way drag does — steeply. Dropping from 100 km/h to 90 km/h on a long towing leg typically recovers a meaningful share of the penalty, and on a 2,000 km trip costs you about two hours. For most caravanners that is the single largest saving available, ahead of tyre pressures, weight reduction or fuel additives.
Two secondary levers are worth the effort: get the van sitting level, since a nose-up attitude presents more area to the airstream, and run the tow vehicle’s tyres at the pressure specified for a loaded vehicle rather than its unladen figure.
Diesel prices vary more by city than most people assume
If your trip crosses state lines, the price you fill at changes. On 19 August 2026 the capital-city diesel averages ran from 241.5 cpl to 248.6 cpl, and regional averages sat above all of them. Plan fills around the cheaper end of the route where the detour is trivial, and expect to pay more once you leave the metropolitan fringe.
Related sections
For the boat that goes on the trailer, see marine fuel planning. For the underlying road-trip maths, see trip planning. There is also a longer guide on caravan fuel consumption in Australia.