Guide
Best time to buy petrol
in Australia
City-by-city breakdown of price cycles and how to time your fill-up.
Written and reviewed by Mark Schreuder, founder of PetrolPulse · First published 23 March 2026 · Last updated 24 July 2026
The short answer: in Perth, fill up on Tuesday. In Sydney, Melbourne, Brisbane and Adelaide there is no fixed cheapest weekday — buy late in the slow price decline, the day before the next jump, because those cities run multi-week cycles rather than a weekly one.
| City | Cycle length (ACCC 2025 avg) | When to fill up |
|---|---|---|
| Sydney | ~5 weeks (ACCC, 2025 average) | The day before the next price jump |
| Melbourne | ~6 weeks (ACCC, 2025 average) | Late in the falling leg of the cycle |
| Brisbane | ~6.5 weeks (ACCC, 2025 average) | Late in the falling leg of the cycle |
| Perth | 1 week (ACCC, 2025 average) | Tuesday |
| Adelaide | ~2.5 weeks (ACCC, 2025 average) | Late in the falling leg of the cycle |
Why timing matters
Petrol prices in Australian cities can vary by 15–25 cents per litre between the cheapest and most expensive point in a single price cycle. For a 50-litre tank, that's a $7.50–$12.50 difference on a single fill-up.
How much of that you can actually capture over a year depends heavily on your city, and it is a lot less than the per-tank figure implies — you would have to hit the bottom of every cycle and never fill at a peak. The ACCC estimates Perth drivers can save up to $520 a year because the weekly cycle gives them roughly 52 chances to time it right. Cities running five- to six-week cycles offer a fraction of those opportunities, so the realistic annual saving there is materially smaller.
Current caveat: the ACCC reports that since the Middle East conflict began in late February 2026, regular price cycles have mostly not occurred in Sydney, Melbourne, Brisbane or Adelaide. The cycle lengths below are 2025 averages and describe how these markets behave normally — check your city's live forecast for what the market is actually doing today.
The key insight is that the day of the week matters far less than where in the cycle you are. A Tuesday in the peak phase is more expensive than a Friday at the trough. PetrolPulse tracks cycle position daily so you always know which situation you're in.
Sydney
Cycle length: ~5 weeks (ACCC, 2025 average)
Best timing
The day before the next price jump
Sydney runs one of the longer discount cycles in Australia, and it has kept stretching — from the textbook fortnight out to an average of about five weeks between peaks across 2025, on ACCC figures. Prices jump 25–35 cents per litre in a single day, then grind down 1–3 cents per day for weeks. That shape means the weekday matters little: the cheapest day is almost always the day before the next jump, which is what the Sydney forecast is built to call.
See Sydney's current forecastMelbourne
Cycle length: ~6 weeks (ACCC, 2025 average)
Best timing
Late in the falling leg of the cycle
Melbourne's cycle has a similar shape to Sydney's — a sharp 10–30 cent jump followed by a long grind down — but it runs longer, averaging about six weeks between peaks across 2025 on ACCC figures. The other difference is the data: Victoria's scheme publishes a daily price cap (the maximum a station has committed to charge that day), not real-time changes, so the listed price is a ceiling and stations may sell below it. Timing the falling leg still works; just expect the occasional pleasant surprise at the bowser.
See Melbourne's current forecastBrisbane
Cycle length: ~6.5 weeks (ACCC, 2025 average)
Best timing
Late in the falling leg of the cycle
Brisbane has the longest discount cycle of the five biggest cities — about six and a half weeks between peaks on average across 2025, on ACCC figures, and far longer than Perth's weekly rhythm. The peak-to-trough swing is typically 20–30 cents per litre, with a sharp single-day jump followed by a slow daily grind down. Cycle timing is set by which major brand breaks ranks and drops first, so checking the current cycle position beats any weekday rule.
See Brisbane's current forecastPerth
Cycle length: 1 week (ACCC, 2025 average)
Best timing
Tuesday
Perth is the exception where the weekday genuinely matters. WA FuelWatch requires retailers to commit to tomorrow's price by 2pm today, locked for a full 24 hours from 6am — a scheme in force since 2001. The result is a strict weekly cycle, the only one left in the five biggest cities. Our own data puts the cheapest day on Tuesday and the dearest on Wednesday, with a day-of-week spread of around 15 cents a litre — by far the largest of any capital. Fill up Tuesday, avoid Wednesday, and use the committed next-day prices on FuelWatch to confirm the trough before it lands.
See Perth's current forecastAdelaide
Cycle length: ~2.5 weeks (ACCC, 2025 average)
Best timing
Late in the falling leg of the cycle
Adelaide has moved in the opposite direction to the east coast. For most of the 2010s it had the longest discount cycle in the country, up to five weeks between troughs; it has since compressed to an average of about two and a half weeks across 2025, on ACCC figures — now the shortest of the four multi-week cities. The peak-to-trough swing is still substantial at 25–35 cents per litre, but the cheap window is shorter than it used to be, so getting the timing call right matters more in Adelaide than almost anywhere else.
See Adelaide's current forecastWhen the cycle guide breaks down
City-level timing guides assume normal market conditions. There are two situations where the cycle alone isn't enough:
Rising oil markets: When Brent crude or the Singapore MOGAS price rises sharply, retail prices across Australia lift to a new, higher range. The cycle continues, but the trough will be higher than last month's trough. Filling up at the "right" day of the week won't protect you from paying 20 cents more than a month ago.
A weakening Australian dollar: Since fuel is imported in USD, a 5–8% drop in AUD/USD over 4–6 weeks adds roughly 8–12 cents per litre to wholesale costs — and eventually retail prices. This often happens alongside global uncertainty that also pushes oil prices up, compounding the effect.
PetrolPulse's weekly market update flags both of these situations when they're active. The recommendation on your city's forecast page incorporates them automatically.
Common questions
What is the best day of the week to buy petrol in Australia?
Only Perth has a reliable weekly answer: our data shows Tuesday is consistently the cheapest day and Wednesday the dearest, a swing of around 15 cents a litre. In Sydney, Melbourne, Brisbane and Adelaide there is no fixed cheapest weekday — those cities run multi-week cycles, so the cheapest day depends on where the cycle currently sits rather than the day of the week.
How do I know when petrol is at the cheapest point in the cycle?
The cheapest point is the day before prices jump back up. Prices grind down slowly for weeks, then rise 25–35 cents a litre in a single day, so the bottom is the last day of the slow decline. You cannot spot that reliably by eye, which is why PetrolPulse tracks each city's cycle position daily and calls whether you are near the trough or should wait.
How long is the petrol price cycle in each city?
On the ACCC's 2025 averages, cycles ran about five weeks in Sydney, six in Melbourne, six and a half in Brisbane, two and a half in Adelaide, and one week in Perth. The ACCC also notes that regular cycles have mostly not occurred in the four eastern capitals since late February 2026, so treat those lengths as how the markets normally behave rather than a live schedule.
How much can I actually save by timing my fill-up?
A single tank filled at the trough instead of the peak saves roughly $7.50–$12.50 on 50 litres. Over a year the realistic saving depends on your city: the ACCC estimates Perth drivers can save up to $520 because a weekly cycle gives about 52 chances to time it right, while cities on five- to six-week cycles offer far fewer, so the annual figure there is materially smaller.
Is it better to buy petrol in the morning or at night?
Time of day makes little difference in most of Australia — price changes are driven by the cycle and by each retailer's daily reset, not by peak-hour demand. The exception is a price-jump day, when many stations lift their price in the morning, so filling the evening before a known jump can save you the increase.