Petrol vs diesel: which is cheaper to run?
At the national averages on 4 Nov, diesel (280.8 c/L) is 41.7c a litre dearer than U91 (239.1 c/L), so a diesel has to use at least 15% less fuel than the petrol version to cost less per km. On official figures the diesel is cheaper to run in 6 of the 6 models sold both ways.
- diesel vs U91, national
- +41.7c
- less fuel diesel needs
- 15%
- models cheaper as diesel
- 6of 6
Example: Kia Sportage at the national averages
ExampleThe diesel version costs less to run
$251.50 a year
Per 100 km: petrol $19.37, diesel $17.69, over 15,000 km a year.
- Petrol: U91 at 239.1 c/L × 8.1 L/100km
- $19.37/100 km
- Diesel: diesel at 280.8 c/L × 6.3 L/100km
- $17.69/100 km
- Diesel fuel use that costs the same per kmThe diesel uses 22% less fuel; at these prices it needs to use 15% less to break even.
- 6.9 L/100km
- Petrol$2,905.06/yr
- Diesel$2,653.56/yrCheaper to run
Example: Kia Sportage at the national averages. The diesel version costs less to run. $251.50 a year. Per 100 km: petrol $19.37, diesel $17.69, over 15,000 km a year.
The diesel version costs less to run · Petrol $19.37 · Diesel $17.69 per 100 km$251.50 a year
DetailsPetrol or diesel: the same model at current prices
What each version costs in fuel over 15,000 km a year at the national average for the grade it takes.
Hyundai Tucson · Diesel $252 less
Petrol 8.1 L/100km $2,905 · diesel 6.3 L/100km $2,654 a year
Kia Carnival · Diesel $705 less
Petrol 9.6 L/100km $3,443 · diesel 6.5 L/100km $2,738 a year
Kia Sorento · Diesel $988 less
Petrol 9.8 L/100km $3,515 · diesel 6.0 L/100km $2,527 a year
Kia Sportage · Diesel $252 less
Petrol 8.1 L/100km $2,905 · diesel 6.3 L/100km $2,654 a year
Mazda CX-60 · Diesel $590 less
Petrol 7.4 L/100km $2,654 · diesel 4.9 L/100km $2,064 a year
Mazda CX-90 · Diesel $844 less
Petrol 8.2 L/100km $3,118 · diesel 5.4 L/100km $2,274 a year
| Car | Petrol version | Diesel version | Petrol a year | Diesel a year | Difference |
|---|---|---|---|---|---|
| Hyundai Tucson | 2.0L petrol 2WD auto, U91, 8.1 L/100km | 2.0L diesel AWD auto, diesel, 6.3 L/100km | $2,905 | $2,654 | Diesel $252 less |
| Kia Carnival | 3.5L V6 petrol, U91, 9.6 L/100km | 2.2L diesel, diesel, 6.5 L/100km | $3,443 | $2,738 | Diesel $705 less |
| Kia Sorento | 3.5L V6 petrol 2WD, U91, 9.8 L/100km | 2.2L diesel AWD, diesel, 6.0 L/100km | $3,515 | $2,527 | Diesel $988 less |
| Kia Sportage | 2.0L petrol 2WD auto, U91, 8.1 L/100km | 2.0L diesel AWD auto, diesel, 6.3 L/100km | $2,905 | $2,654 | Diesel $252 less |
| Mazda CX-60 | 3.3L turbo petrol AWD, U91, 7.4 L/100km | 3.3L turbo diesel AWD, diesel, 4.9 L/100km | $2,654 | $2,064 | Diesel $590 less |
| Mazda CX-90 | 3.3L turbo petrol AWD, P95, 8.2 L/100km | 3.3L turbo diesel AWD, diesel, 5.4 L/100km | $3,118 | $2,274 | Diesel $844 less |
Fuel use is the official combined lab figure from the Green Vehicle Guide (Australian Government), checked 18 Oct 2026; real driving uses more. Priced at the national U91, diesel, P95 averages, updated .
Diesel against U91 in each capital
The smaller the diesel premium over U91, the less fuel a diesel has to save to cost less per km.
Hobart · diesel +38.0 c/L
U91 243.9 c/L · diesel 281.9 c/L · diesel must use 13% less fuel
Perth · diesel +39.9 c/L
U91 231.3 c/L · diesel 271.2 c/L · diesel must use 15% less fuel
Canberra · diesel +40.4 c/L
U91 244.5 c/L · diesel 284.9 c/L · diesel must use 14% less fuel
Darwin · diesel +41.8 c/L
U91 244.4 c/L · diesel 286.2 c/L · diesel must use 15% less fuel
Melbourne · diesel +42.2 c/L
U91 235.1 c/L · diesel 277.3 c/L · diesel must use 15% less fuel
Brisbane · diesel +43.9 c/L
U91 234.3 c/L · diesel 278.2 c/L · diesel must use 16% less fuel
Adelaide · diesel +44.0 c/L
U91 225.5 c/L · diesel 269.5 c/L · diesel must use 16% less fuel
Sydney · diesel +48.5 c/L
U91 232.4 c/L · diesel 280.9 c/L · diesel must use 17% less fuel
| Capital | U91 average | Diesel average | Diesel vs U91 | Diesel must use |
|---|---|---|---|---|
| Hobart | 243.9 c/L | 281.9 c/L | +38.0 c/L | 13% less fuel |
| Perth | 231.3 c/L | 271.2 c/L | +39.9 c/L | 15% less fuel |
| Canberra | 244.5 c/L | 284.9 c/L | +40.4 c/L | 14% less fuel |
| Darwin | 244.4 c/L | 286.2 c/L | +41.8 c/L | 15% less fuel |
| Melbourne | 235.1 c/L | 277.3 c/L | +42.2 c/L | 15% less fuel |
| Brisbane | 234.3 c/L | 278.2 c/L | +43.9 c/L | 16% less fuel |
| Adelaide | 225.5 c/L | 269.5 c/L | +44.0 c/L | 16% less fuel |
| Sydney | 232.4 c/L | 280.9 c/L | +48.5 c/L | 17% less fuel |
Each capital’s daily average, updated .
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Petrol vs diesel questions
Is diesel cheaper to run than petrol?
Only when the diesel uses enough less fuel. Diesel averages 280.8 c/L nationally, 41.7c a litre dearer than U91 (239.1 c/L), so it needs to use at least 15% less fuel to cost less per km. On official figures that holds for 6 of the 6 models sold both ways.
How do I work out petrol vs diesel fuel cost?
Multiply each version’s L/100km by its price per litre and divide by 100 for the cost per 100 km. At the current national averages a petrol car using 10 L/100km of U91 costs $23.91 per 100 km and a diesel using 8 L/100km costs $22.46, $217 a year less for the diesel over 15,000 km.
Which model saves the most as a diesel?
Of the models sold both ways, the Kia Sorento diesel (6.0 L/100km) saves the most against its petrol version (9.8 L/100km): $988 a year over 15,000 km at the current national averages.
Where is diesel closest to the petrol price?
Hobart: diesel averages 281.9 c/L against 243.9 c/L for U91. The widest gap is in Sydney, 48.5c a litre dearer than U91.
Does the purchase price matter?
Yes. A diesel version often costs more to buy. Enter the price difference in the calculator to see how many years of fuel savings it takes to pay it back. Servicing, rego and resale are not included.