Petrol prices dominate headlines whenever they spike, but most Australians don't know what their car actually costs to run per kilometre, per month, or per year. Getting that number right is essential for budgeting, comparing vehicles, evaluating EVs, and deciding whether a job's salary is really worth the commute.
Try it yourself: Use our free Fuel Cost Calculator to calculate fuel costs per kilometre, per week, and per year — and compare different vehicles or fuel types.
The Fuel Cost Formula
Fuel cost per km = (Fuel consumption L/100km ÷ 100) × Price per litre
Annual fuel cost = Fuel cost per km × Annual kilometres driven
Cost per trip = Distance (km) × Fuel cost per km
Example: Toyota Corolla, 7.5L/100km, petrol at $2.05/L, 15,000 km/year
- Fuel cost per km: (7.5 ÷ 100) × $2.05 = 15.4 cents/km
- Annual fuel cost: 15.4c × 15,000 = $2,306/year
- Weekly: $2,306 ÷ 52 = $44/week
Average Fuel Consumption by Vehicle Type
| Vehicle Type | Typical Consumption (L/100km) | Annual Cost (15,000 km @ $2.00/L) |
|---|---|---|
| Small city car (e.g. Mazda 2) | 5.5–6.5 | $1,650–$1,950 |
| Medium sedan (e.g. Camry) | 6.5–8.5 | $1,950–$2,550 |
| Small SUV (e.g. RAV4) | 7.0–9.0 | $2,100–$2,700 |
| Large SUV / 4WD | 10.0–14.0 | $3,000–$4,200 |
| Ute (e.g. HiLux) | 9.0–12.0 | $2,700–$3,600 |
| Hybrid (e.g. RAV4 Hybrid) | 4.5–6.0 | $1,350–$1,800 |
| Plug-in hybrid (city driving) | 1.5–3.0 | $450–$900 |
| Electric vehicle | 0 (electricity only) | $500–$900 (electricity) |
Australian Petrol Prices: Understanding the Cycle
Australian petrol prices follow a well-documented price cycle — particularly in major cities — where prices drop over several days then spike sharply. This is not random; it's coordinated industry behaviour allowed under competition law.
The typical petrol price cycle in Australian cities (especially Sydney, Melbourne, Brisbane, Perth, Adelaide):
- Prices spike to their highest point typically on a Wednesday or Thursday
- Prices then decline gradually over 10–14 days
- Buying at the bottom of the cycle (often Tuesday or Sunday) can save 15–25 cents per litre compared to the peak
- GasBuddy, PetrolSpy, and state-based apps (FuelWatch in WA) track real-time prices by suburb
Price cycle savings example:
50L tank fill: Peak price $2.25/L vs. trough $2.00/L
Saving per fill: $12.50. With monthly fill-ups: $150/year
With weekly fills: $650/year — significant for high-mileage drivers.
Petrol vs. Diesel vs. Premium: Which Should You Use?
Regular Unleaded (E10 / 91 RON)
The baseline fuel for most passenger vehicles. E10 (10% ethanol blend) is typically 2–4 cents per litre cheaper than 91 RON but produces slightly less energy per litre — fuel economy drops 1–3%, often negating the price advantage. Check your owner's manual — some vehicles specifically prohibit E10.
Premium (95 and 98 RON)
Required for many turbocharged and high-performance engines. For vehicles that recommend but don't require premium, the economy improvement from higher octane often doesn't offset the price premium (typically 15–25 cents/L more than 91). For vehicles that require premium, using lower octane can cause engine damage.
Diesel
More energy per litre than petrol, so diesel vehicles typically achieve 10–20% better fuel economy on equivalent journeys. Diesel suits high-mileage drivers and towing applications. Disadvantages: higher purchase price, DPF maintenance costs, and poor efficiency in short stop-start city driving.
The True Cost Per Kilometre (Beyond Fuel)
Fuel is only part of the per-kilometre running cost. The ATO's 2025–26 rate of 88 cents per kilometre is designed to capture all running costs:
| Cost Component | Typical % of Total | At 15,000 km/yr |
|---|---|---|
| Fuel | 25–35% | $2,000–$2,800 |
| Depreciation | 30–40% | $2,400–$3,200 |
| Insurance | 10–15% | $800–$1,200 |
| Registration | 5–8% | $400–$640 |
| Servicing / tyres | 10–15% | $800–$1,200 |
| Total | 100% | $6,400–$9,040 |
Petrol vs. EV: The Running Cost Comparison
For the fuel cost component specifically, an EV running on home-charged electricity typically costs 2–4 cents per km to run, versus 14–20 cents per km for a petrol vehicle. At 15,000 km per year:
EV vs petrol annual fuel/energy cost:
- Petrol mid-sized SUV (9L/100km, $2.00/L): $2,700/year
- EV equivalent (17kWh/100km, 25c/kWh home charging): $638/year
- Annual saving: $2,062
For a $15,000 EV price premium, payback from fuel savings alone: ~7 years. Add reduced servicing costs and it improves further.
Frequently Asked Questions
How do I calculate how much petrol I'll need for a road trip?
Litres needed = (Trip distance km ÷ 100) × Vehicle consumption (L/100km). Add 10–15% buffer for hills, AC, and headwinds. At 8L/100km for a 1,200km trip: (1,200 ÷ 100) × 8 = 96 litres needed.
How can I improve my fuel economy?
The most effective techniques: maintain correct tyre pressure (under-inflation increases fuel use 1–2%), smooth acceleration and braking (aggressive driving increases consumption 15–30%), reduce air conditioning where practical, remove roof racks when not in use (adds 5–10% drag at highway speeds), and drive at or just below the speed limit (aerodynamic drag increases exponentially with speed).
What fuel does my car take?
Check the inside of your fuel cap — it will state the minimum octane rating or fuel type required. Alternatively, your owner's manual specifies this. Using the wrong fuel type can damage modern engines.
Calculate your fuel costs
Use our Fuel Cost Calculator to calculate your running costs per km, weekly fuel spend, and annual fuel bill — and compare petrol versus EV running costs.
Also explore: EV vs Petrol Calculator · Commute Cost Calculator