South Australia Diesel Climbs 8 Cents in a Fortnight as the ACT Emerges as the Nation's Cheapest
According to pricing data collected at 2pm AEST on Saturday 15th August 2026, diesel in South Australia averages 249.4 cents per litre across 375 reporting sites, dearer than in any eastern state and within a cent of the national leader. The 3.3 cent rise on the day was the largest single day move of any Australian state, and it caps a fortnight of increases for SA motorists.
The comparison with a fortnight ago is the part worth dwelling on. When I last analysed South Australian diesel on 2nd August 2026, the state averaged 241.1 cents across 370 sites, and Riverland towns such as Barmera were holding near 222. Thirteen days later the statewide average has added 8.3 cents and the cheapest diesel reported anywhere in SA sits at 228.5. Even the price floor has lifted by around six cents in under two weeks.
Where South Australia now sits
NSW eased 2.1 cents on Saturday to average 246.8, while Victoria added 1.0 cent to land on exactly the same figure. Queensland rose 1.5 cents to 248.3, and Western Australia, which I reported climbing 17.5 cents in a single day earlier this month, moved 1.8 cents lower to 250.1. That leaves South Australia at 249.4, above every eastern state and just 0.7 of a cent behind WA. The two averages are heading toward each other. If both trends continue, SA could hold the dearest diesel average of the major states within days.
The ACT sits at the other end of the table. Diesel across the territory's 23 reporting sites averages 243.2 cents, the cheapest of any state or territory, and the range is unusually narrow. The dearest servo charges 247.9 while the cheapest sits at 236.9, a spread of just 11 cents. Compare that with South Australia, where the gap between the cheapest site at 228.5 and the dearest at 350.0 stretches to 121.5 cents. Canberra drivers gain relatively little from shopping around. For SA drivers, checking current diesel prices before filling up can be worth more than 20 cents a litre.
Regional SA is not moving as one
The state's regional centres are behaving very differently from one another. Premium unleaded 98 in Mount Gambier fell 7.4 cents to average 220.5 across six sites, while the same fuel in Clare rose by exactly 7.4 cents to 228.6 across five sites. Identical magnitude, opposite directions.
That is the reverse of what I documented in regional Victoria earlier this week, where Ballarat, Ararat, Bendigo and Moe all reset upward together. South Australia's towns appear to move on their own schedules rather than in a coordinated cycle, which makes town by town comparison far more useful for anyone driving between regional centres.
What it means at the pump
The fortnight of increases is consistent with higher wholesale costs flowing through to South Australian forecourts later than they reached the eastern states, which recorded their sharpest diesel movements earlier in August. Whether the SA average pushes past Western Australia's 250.1 is the figure to watch over the coming week, and the price trends data will show that move as it happens.
For motorists in Adelaide and across regional SA, the practical takeaway has not changed. Location and timing remain the two levers that matter in fuel savings. With a 121.5 cent gap between the state's cheapest and dearest diesel, this fortnight they matter in South Australia more than anywhere else in the country.
