Diesel in 2026, and what the excise did

If you run a diesel boat, a diesel tow vehicle or both, 2026 has been an expensive year. Two lines in our October and November emails need straightening out, and here's the picture behind them.

The peak was March, not April

According to the ACCC's weekly fuel monitoring, retail prices across Australia's five largest cities (Sydney, Melbourne, Brisbane, Adelaide and Perth) were around their highest on 31 March 2026, a month after the conflict involving the United States, Israel and Iran escalated in late February. The ACCC notes Australia relies heavily on Asian refineries for diesel, and those refineries run on Middle Eastern crude, so the price came through quickly.

Where prices sat in late September

The ACCC's report of 24 September gave these figures for 23 September (five largest cities, daily average):

• Diesel: 286.8 c/L. That's 18.9 c/L higher than a week earlier, a rise of about 7%. It's 35.6 c/L below the 31 March peak but 110.2 c/L above 20 February, before the conflict.
• Regular unleaded: 237.1 c/L. That's 12.9 c/L higher in a week, 20.1 c/L below the March peak and 66.2 c/L above February.
• Regional areas (more than 190 towns the ACCC monitors): diesel 288.9 c/L, petrol 242.7 c/L.

So diesel is below its high, but the direction at the end of September was up, not down. The ACCC put the rise down to international refined fuel prices, which stayed high while the conflict went on.

What the excise did

The federal government cut fuel excise twice this year, and it's now back in full:

• 1 April to 30 June: excise cut by 32 c/L, roughly half the normal rate.
• 1 July to 2 August: the cut shrank to 16 c/L.
• From 3 August: excise fully restored. The ACCC gives the full rate as 53.7 c/L.

The ACCC's view is that fuel businesses generally passed the excise changes through to pump prices properly, both when the cut came in and when it was wound back. In other words, part of the drop you saw in April was the tax cut, and part of the rise from July was the tax coming back. The rest is the world oil price.

What it means on the water

Diesel prices hit boaties twice if you also tow with a diesel ute.

• Fill the tow vehicle in town. Regional diesel averaged a couple of cents a litre more than the big cities in late September, and marina fuel docks usually charge more again.
• Use a price app. The ACCC keeps telling people to shop around. Prices can differ widely between servos in the same suburb, and on a 100-litre fill the gap adds up.
• Trim and weight. Running trimmed out, with clean props and a clean hull, and without a full water tank you don't need, saves fuel at any price.
• Know your burn. Work out litres per hour at your usual cruising revs and plan the trip around it, with a reserve of about a third.

Watch this space

Fuel prices move every week. We've used the ACCC's 23 September figures. If you're reading this later, check the latest ACCC or Australian Institute of Petroleum weekly report for current numbers.

Sources

• accc.gov.au — 23 Sept prices (petrol 237.1 c/L, diesel 286.8 c/L, 5 largest cities); +18.9 c/L in a week; peak around 31 March; vs 20 Feb; regional 288.9 c/L; excise timeline and 53.7 c/L full rate from 3 Aug; weekly reports directed to 30 Sept
• accc.gov.au — 29th weekly report page
• accc.gov.au — 32 c/L cut 1 April–30 June; 16 c/L cut 1 July–2 August
• aip.com.au — AIP weekly petrol and diesel reports (latest week ending 27 Sept 2026)
• abc.net.au — cut ended at midnight 2 August (headline, search result)

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