Australia's eight capital cities buy fuel from the same benchmark, pay the same excise and are served by the same wholesalers, but the price you pay depends heavily on which city you are in and which day of the cycle you fill up. In Perth the difference between Tuesday and Wednesday can be 15 cents a litre. In Melbourne the gap between the cheapest and dearest site on a single morning was 52 cents. This guide covers where each capital sat at the end of August 2026 and how the cycles work.
All prices are ACCC daily averages for regular unleaded (91) and regular diesel on Tuesday 26 August 2026, from the ACCC's 28 August weekly monitoring report. Same-day ranges are as at 11 am and exclude membership-only sites.
Capital city prices on 26 August 2026
Regular unleaded (cents per litre), with the cheapest and dearest site on the day:
- Brisbane 202.7 (range 187.9 to 214.9)
- Sydney 203.1 (188.7 to 219.7)
- Adelaide 203.5 (193.5 to 210.9)
- Hobart 206.4 (195.7 to 220.9)
- Melbourne 206.7 (187.9 to 239.9)
- Canberra 209.6 (199.9 to 212.9)
- Darwin 210.7 (208.5 to 215.5)
- Perth 211.5 (186.9 to 226.9), a Wednesday cycle peak; Tuesday's average was 196.9
Regular diesel:
- Perth 246.1
- Sydney 248.8
- Adelaide 249.7
- Melbourne 253.3
- Brisbane 253.3
- Darwin 253.7
- Hobart 255.2
- Canberra 261.6
The five-city average was 205.5 for petrol and 250.2 for diesel, and diesel sat about 45 cents above petrol in every city. That gap is unusual by historical standards; on 20 February, a week before the Middle East conflict escalated, diesel was only 6 cents dearer than petrol across the five cities. The Middle East is a disproportionate supplier of diesel and of the crude grades that yield the most diesel, and Asian refineries that supply Australia were built around those crudes, so the diesel benchmark rose far more than petrol and has been slower to fall.
What the same-day ranges tell you
The range within a city on a single morning is the most useful number on this page. In Melbourne a driver who filled at the cheapest site paid 52 cents a litre less than one at the dearest, about $28 on a 55-litre tank. Perth's spread was 40 cents, Sydney's 31, Brisbane's 27. Only Darwin (7 cents) and Canberra (13 cents) had narrow ranges, which is consistent with their lack of price cycles and thinner competition.
Those spreads are why the ACCC's standing advice is to use a price app before every fill rather than trying to predict the market.
How petrol price cycles work
In Sydney, Melbourne, Brisbane, Adelaide and Perth, regular unleaded prices move in a sawtooth: a sharp rise over a day or two, then a slow slide over the following weeks until the next jump. The ACCC is explicit that these cycles are the product of retailer pricing decisions, not wholesale costs, and that not every retailer joins in. Premium 95 and 98 and E10 generally move with 91. Diesel and LPG do not cycle at all, and neither do Canberra, Hobart, Darwin or most regional towns.
Average cycle lengths in 2025:
- Perth: 1 week. Prices bottom on Tuesday, jump on Wednesday.
- Adelaide: about 2.5 weeks.
- Sydney: about 5 weeks, typically 12 to 16 days rising then 2 to 4 weeks falling.
- Melbourne: about 6 weeks.
- Brisbane: about 6.5 weeks.
The eastern-city cycles have been erratic since February 2026. The ACCC reported that cycles mostly did not occur in Sydney, Melbourne, Brisbane or Adelaide after the conflict began, because wholesale prices were moving too fast for the usual retail pattern to establish itself. Perth's regulated weekly cycle kept running throughout. As international prices stabilise, the eastern cycles are expected to re-establish, and the ACCC publishes a buying tip for each of the five cities three times a week saying whether prices are near the top or bottom.
Perth: the cycle you can set a watch by
Western Australia's FuelWatch scheme requires every retailer to notify tomorrow's price by 2 pm today and to hold it for 24 hours. The state government publishes an alert every Tuesday afternoon telling motorists to fill up before the Wednesday rise. On 26 August the average rose 14.6 cents from the Tuesday, although the ACCC noted 30 sites were still selling below 192 cents on the Wednesday. If you live in Perth, the rule is simple: fill on Tuesday, never on Wednesday.
Melbourne: the new 24-hour lock
Since March 2026, Victorian retailers must report a maximum price for each 24-hour period by 2 pm the day before and can only lower it during that day, never raise it. It is modelled on FuelWatch and is designed to eliminate mid-day price jumps. The data is published through Servo Saver in the Service Victoria app, though the public feed runs a day behind. The ACCC has estimated that Melbourne motorists who consistently buy at the low point of the cycle could save around $333 a year.
Sydney and Brisbane: long cycles, real-time data
NSW has run FuelCheck, a genuine real-time system, since 2016; Queensland has mandated reporting since 2018 but leaves the display to third-party apps. With cycles of five to seven weeks, the trick in these cities is to watch the trend: buy when the ACCC tip says prices are near the bottom, and when the jump comes, fill at the independents that are slowest to raise. During the falling phase the gap between the cheapest and dearest sites is at its widest, which is when a price app earns its keep.
Adelaide: short cycles, tight range
Adelaide's cycles ran two to four weeks in 2025 and its same-day price range is the narrowest of the big five. It has often been the cheapest capital in calm periods (161.3 on 20 February 2026), and it recorded one of the largest rises through the crisis.
The smaller capitals
Canberra, Hobart and Darwin have no cycle, so there is no cheap day to target. What they do have is a stable ranking: Canberra above Sydney despite sharing its wholesale supply, Hobart a few cents above the mainland because every litre arrives by ship, and Darwin consistently near the top for petrol. In these cities the only lever is the site-to-site spread, and Darwin's is small.
What it costs to get it wrong
On a 55-litre tank, 15 cents a litre is $8.25. A driver filling weekly at the wrong point of a Perth cycle, or at the dear end of a Melbourne range, gives away several hundred dollars a year. Supermarket dockets (typically 4 cents a litre) and fuel-company loyalty schemes are worth using but are small next to cycle timing.
FAQs
Which capital city has the cheapest fuel?
It changes weekly. On 26 August 2026 Brisbane was cheapest for petrol and Perth for diesel. In quieter periods Adelaide and Perth (on a Tuesday) are frequently the cheapest.
Why are petrol price cycles legal?
Because they are independent pricing decisions by retailers rather than an agreement between them. The ACCC monitors them and would act on evidence of collusion, but has repeatedly found the cycles are a competitive pricing pattern rather than a cartel.
Does diesel have a price cycle?
No. Diesel prices track wholesale movements and do not show the sawtooth pattern. Nor does LPG.
Are the cycles back to normal after the 2026 crisis?
Not fully as of late August 2026. Perth's weekly cycle never stopped; the eastern cities' cycles largely disappeared from March and were only beginning to re-form. Check the ACCC's buying tips, updated Monday, Wednesday and Friday.
What is the best fuel price app?
The official state app where one exists: FuelCheck for NSW, ACT and Tasmania, FuelWatch for WA, MyFuel NT, and Servo Saver for Victoria. PetrolSpy and MotorMouth combine every state's feed into one app and are the practical choice for Queensland and South Australia, which publish data but run no app of their own.