Taking the tax out
The terminal gate price includes two taxes. Excise is a fixed amount per litre, and GST is one eleventh of the price. Take both out and you are left with the cost of the fuel itself at the terminal, meaning the refined petrol or diesel, delivered to Australia and stored, plus the wholesaler's margin. Put that next to the cost of the crude oil in a litre, converted to Australian cents, and the gap between them is everything that happens between an oil well and the terminal.
We did this for every weekday in 2026, using the national average terminal gate price, the excise rate in force on each day, and Brent crude converted at that day's exchange rate.
| Month, 2026 | Brent, c/L | Petrol before tax | Gap | Diesel before tax | Gap |
|---|---|---|---|---|---|
| February | 62.3 | 86.9 | 24.5 | 95.5 | 33.2 |
| March | 96.1 | 138.6 | 42.6 | 174.1 | 78.0 |
| April | 88.9 | 155.5 | 66.6 | 226.3 | 137.4 |
| May | 89.8 | 141.0 | 51.2 | 171.6 | 81.8 |
| June | 74.9 | 122.1 | 47.2 | 142.5 | 67.6 |
| July | 76.5 | 117.7 | 41.1 | 143.6 | 67.1 |
| August | 78.0 | 124.4 | 46.4 | 164.0 | 86.0 |
| September | 89.3 | 143.3 | 54.0 | 179.2 | 89.9 |
| October | 92.0 | 159.7 | 67.7 | 186.1 | 94.1 |
Cents a litre, monthly averages. Wholesale is the national average terminal gate price less GST and the excise rate in force each day. Gaps may not subtract exactly because of rounding. October is 1 to 7 October.
What the gap shows
In February, wholesale petrol cost about 25c a litre more than the crude it was made from, and diesel about 33c. In April the diesel gap reached 137c. It has never returned to where it was.
Crude did most of its rising in March, when Brent jumped from about US$70 to over US$100. After that, crude in Australian dollars actually fell for most of the year, to 75c a litre in June, and is only now back near its March level. The cost of refined fuel did not follow it down nearly as far. That is why, in June, petrol was still 35c a litre dearer before tax than in February even though crude was only 13c dearer.
Why refined fuel got so expensive
The gap is mostly the refining margin, also called the crack spread, which is the price refiners can get for petrol and diesel over what they pay for crude. It also includes shipping, insurance, storage at the terminal and the wholesaler's own margin, which are small and stable in normal times.
Several things pushed it up in 2026.
- Product, not just crude, was disrupted. The Gulf exports refined fuel as well as crude, and the refineries in Asia that supply Australia depend on Gulf crude. When supply through the Strait of Hormuz was disrupted, refined fuel was squeezed from both ends.
- Diesel was already tight. Europe lost its Russian diesel supply after 2022 and has bid for diesel from everywhere since, including Asia. Freight, mining and farming worldwide run on it, so demand barely falls when the price rises.
- Shipping and insurance costs rose. Tankers moving through or near a conflict zone cost more to charter and insure, and that cost is passed on per litre.
- Talk of a US diesel export ban in September added to the fear of scarcity in the one product the world is shortest of.
Why Australia feels it more
With only two refineries left, at Lytton and Geelong, Australia imports most of its petrol, diesel and jet fuel. Our wholesale prices are set off the price of refined fuel in Singapore, not off the price of crude. So when refining margins blow out, there is no local refinery margin to cushion it. We pay the regional price for the finished product, plus the cost of shipping it here.
That is also why the price of crude alone is a poor guide to the bowser in a year like this one. On our market page we show Brent in Australian dollars because over most years it explains most of the movement. In 2026 it explained less than half.
What to watch
- If the gap closes towards its February level while crude holds steady, wholesale petrol has room to fall by 30c a litre or more before tax, and diesel by 50c or more. That would happen if refined fuel supply from the Gulf and Asia normalises.
- If crude falls but the gap does not, prices at the pump will fall much less than the headlines about oil suggest. That was the story of June and July.
- Diesel's gap is the one to watch for anyone running a business. It has stayed above 65c every month since March.
We will update this table each month in our monthly reports.
Where these figures come from
Wholesale prices are the terminal gate prices published each weekday by the Australian Institute of Petroleum, which we hold back to 2004. The national figure is AIP's own average where it has published one, and our weighted calculation in between, which matches AIP's to within 0.1c. Oil and currency prices are delayed market closes. Excise rates are the ATO's. We check every figure against that data before publishing and correct mistakes in the update log. Spotted one? Email hello@thepetrolprice.com.