Fuel-efficient used cars under $15,000
Compare used-car model families with under-$15,000 examples by exact-variant fuel use, annual cost and pre-purchase checks.
Car fill-up cost by tank size (2026)
Estimate a full tank or partial fill from litres added, tank capacity, pump price and the fuel grade required by your vehicle.
By the FuelRadar team1 min read
The fill-up cost formula
Multiply the litres you expect to add by the pump price in dollars per litre. If you plan to add 50 litres and the required fuel is $1.85/L, the estimate is 50 x 1.85, or $92.50. Pump prices are shown in cents per litre, so divide by 100 before using the formula.
Example fill sizes
| Litres added | At $1.85/L | At $2.05/L |
|---|---|---|
| 30L | $55.50 | $61.50 |
| 40L | $74.00 | $82.00 |
| 50L | $92.50 | $102.50 |
| 60L | $111.00 | $123.00 |
| 80L | $148.00 | $164.00 |
Tank capacity is not the usual fill amount
The nominal tank capacity comes from the manufacturer for a specific model year and variant. A normal fill is usually smaller because fuel remains in the tank. Use litres added for a receipt check and use the manufacturer capacity only for a full-tank budget estimate.
Why the price gap matters more on larger fills
A 10c/L difference changes 40 litres by $4, 60 litres by $6 and 80 litres by $8. Use the litres you expect to buy when deciding whether a lower-priced station is worth the detour.
Use the correct fuel grade
Check the owner's manual or fuel-flap label. If the vehicle requires P95, P98 or diesel, do not estimate the fill with a cheaper U91 or E10 price. Tank capacity can also differ between variants, so confirm both details for the exact vehicle.
Check the current local price
Search your suburb, select the required fuel grade and compare nearby station prices and update times. Confirm the final price at the bowser before filling.
Common questions
How do I calculate the cost to fill my car?
Multiply your tank size in litres by the price per litre. For a real top-up, multiply the litres added by the pump price on the receipt.
Why does my fill cost change so much?
Tank size is fixed, but pump prices move by suburb, station, fuel grade and price-cycle timing. A few cents per litre matters more on large tanks.
Should I estimate using U91, E10, diesel or premium?
Use the grade your vehicle actually takes. Premium and diesel can price differently from U91 and E10, so a generic unleaded average can understate the fill cost.
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