Petrol Cost Per Km Australia 2025 — Calculator & Car Comparison

What Is Petrol Cost Per Km?

Petrol cost per km is the single most useful number for understanding what your car actually costs to drive. It answers the practical question: how much do I spend on fuel every time I travel one kilometre?

Unlike sticker price or insurance premiums, your cost per km changes constantly — it rises when petrol prices spike, falls when you drive more efficiently, and differs dramatically between vehicle types. A small hatchback and a diesel ute can have a 2× difference in fuel cost per km even when refuelling at the same bowser.

Knowing your petrol cost per km lets you:

• Accurately calculate the true cost of any trip before you leave
• Compare the real operating cost of different vehicles
• Quantify how much a fuel price rise affects your weekly budget
• Decide whether an EV or hybrid makes financial sense for your situation
• Claim a correct vehicle allowance for work-related driving (the ATO cents-per-km rate for 2025–26 is $0.88/km, but your actual fuel cost is only a portion of that)

The Formula: How to Calculate Petrol Cost Per Km

The calculation is straightforward:

Cost per km = (L/100km × Price per litre) ÷ 100

Worked examples:

• Toyota Corolla (8.5 L/100km) at $1.95/L: (8.5 × 1.95) ÷ 100 = $0.166/km
• Toyota HiLux (11.5 L/100km) at $2.05/L: (11.5 × 2.05) ÷ 100 = $0.236/km
• Mazda 3 (7.5 L/100km) at $1.90/L: (7.5 × 1.90) ÷ 100 = $0.143/km

The formula scales linearly — a 10% rise in petrol price increases your cost per km by exactly 10%. A 10% improvement in fuel economy reduces your cost per km by 10%.

Australian Average Fuel Economy

The Bureau of Infrastructure and Transport Research Economics (BITRE) reports that the average new passenger car sold in Australia uses around 7.5–9 L/100km under official test conditions. Real-world consumption is typically 10–20% higher. For planning purposes, these are reliable benchmarks:

• City driving: 12 L/100km average (stop-start traffic, air conditioning, short trips)
• Highway driving: 8 L/100km average (steady speed, minimal idling)
• Combined cycle: 10 L/100km average (typical mixed use)

These averages cover mainstream petrol sedans and hatchbacks. SUVs and utes consume significantly more; small city cars and hybrids significantly less.

Petrol Cost Per Km Table: All Combinations

The table below shows cost per km (in cents) for common Australian petrol prices ($1.70–$2.20/L) across a range of fuel economies. Find your car's L/100km on the left and your local price across the top.

To use this table: find your row (fuel economy), read across to your petrol price column. That cell is your fuel cost per km in cents. Multiply by 100 to get the cost per 100 km in dollars.

Popular Australian Cars: Petrol Cost Per Km Compared

Here is how Australia's best-selling cars compare on fuel cost per km, using a petrol price of $1.95/L as a baseline — close to the 2025 national average for 91 RON unleaded.

The difference between the most and least efficient vehicles here is significant: a Mazda 3 driver spends over $1,170 less per year on fuel than a HiLux driver covering the same distance. Over a 5-year ownership period, that gap exceeds $5,800 — a meaningful factor in total cost of ownership.

EV vs Petrol: Cost Per Km Comparison

Electric vehicles have transformed the cost-per-km equation for Australian drivers. While petrol cars typically cost $0.15–$0.25/km in fuel alone, EVs cost a fraction of that — especially when charged at home on off-peak electricity.

Even at standard home electricity rates, EVs cost roughly $0.04–$0.05/km — about 3–5× cheaper per km than the average petrol car. At off-peak rates with a solar system, EV fuel cost can fall below $0.02/km.

For a driver covering 15,000 km/year, switching from a 10 L/100km petrol car to an EV charged mostly at home saves approximately $2,250–$2,625 per year in fuel costs alone. That saving needs to be weighed against the higher purchase price and depreciation of the EV.

Annual Fuel Cost: What Does 15,000 km Actually Cost You?

The average Australian driver travels approximately 13,000–15,000 km per year. Here is what that distance costs at various fuel efficiencies, calculated at $1.95/L:

These figures are fuel costs only — they do not include registration, insurance, tyres, servicing, or depreciation. A full picture of your annual running costs will be 3–4× higher than fuel alone. Use our Car Running Costs Australia guide for a complete breakdown.

7 Ways to Reduce Your Petrol Cost Per Km

You cannot control the price at the pump, but you can control how many litres your car needs per kilometre. Each of these measures has a meaningful, measurable effect on your fuel economy:

1. Maintain Correct Tyre Pressure

Under-inflated tyres increase rolling resistance, which directly raises fuel consumption. Driving on tyres 10 PSI below the recommended pressure increases fuel use by approximately 1–3%. Check your door jamb or owner's manual for the correct pressure, and check monthly — tyres naturally lose 1–2 PSI per month.

2. Accelerate and Decelerate Smoothly

Aggressive acceleration is the single biggest driver of excess fuel consumption in city driving. Anticipating traffic flow, accelerating gently, and coasting to a stop instead of braking hard can reduce fuel consumption by 10–20% in urban conditions. Modern fuel-injected cars use virtually zero fuel when decelerating with the engine in gear — so coasting down to a red light burns nothing.

3. Drive at the Optimal Speed on Highways

Aerodynamic drag increases with the square of speed. Most modern petrol cars are most efficient between 80–100 km/h. Driving at 110 km/h instead of 90 km/h typically increases fuel consumption by 15–20%. On a long highway trip, slowing down 10 km/h can save 1–2 L/100km — around $15–$25 per 1,000 km.

4. Remove Excess Weight and Roof Racks

Every extra 100 kg of weight increases fuel consumption by roughly 0.5 L/100km. Empty roof racks add aerodynamic drag equivalent to 0.2–0.5 L/100km at highway speeds. Remove roof boxes and racks when not in use — it is a free fuel saving.

5. Service Your Car Regularly

Fresh engine oil, a clean air filter, and properly functioning fuel injectors all contribute to optimal combustion efficiency. A clogged air filter alone can increase fuel consumption by 10%. Sticking to the manufacturer's service schedule is not just about reliability — it is also a direct fuel economy measure.

6. Use the Air Conditioning Strategically

Air conditioning increases fuel consumption by 1–2 L/100km in city conditions. At speeds below 60 km/h, opening windows is more fuel-efficient than running the A/C. At highway speeds above 80 km/h, the aerodynamic drag from open windows is worse than the A/C load — so close the windows and use A/C at motorway speeds.

7. Time Your Petrol Purchases

In most Australian capital cities, petrol prices follow a weekly cycle with lows typically mid-week (Tuesday–Wednesday) and peaks Thursday–Saturday. Filling up on the cheap day of the cycle can save $0.12–$0.22 per litre — a $6–$13 saving per 60-litre fill. Read our full guide: Best Time to Buy Petrol in Australia.

Related Calculators

• Trip Fuel Cost Calculator — calculate fuel cost for any trip by distance and fuel economy
• Commute Fuel Cost Calculator — find your weekly and annual commute fuel spend
• Fuel Economy Savings Calculator — see exactly how much a more efficient car saves you
• EV vs Petrol Calculator — full lifetime cost comparison including purchase price
• Fuel Budget Planner — set a monthly fuel budget and track your spend