Guide
Best time to buy petrol
in Australia
City-by-city breakdown of price cycles and how to time your fill-up.
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 $7–12 difference on every fill-up. Over a year of weekly fill-ups, timing your purchases to the trough rather than the peak saves $350–600 per vehicle.
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. PetrolCast tracks cycle position daily so you always know which situation you're in.
Sydney
Cycle length: 6–8 weeks
Best timing
Tuesday to Thursday
Sydney runs one of Australia's most pronounced price cycles. Prices typically spike on Thursday or Friday and fall through the following week, hitting a trough around Tuesday to Thursday. The cycle resets roughly every 6 to 8 weeks. During the trough, prices can be 15–25 cents per litre lower than the peak — a significant saving over a full tank.
See Sydney's current forecastMelbourne
Cycle length: 6–8 weeks
Best timing
Tuesday to Thursday
Melbourne's cycle closely mirrors Sydney's. The pattern is driven by the same major retail chains and runs on a similar 6-8 week rhythm. Tuesday through Thursday in the low phase of the cycle is typically the best window. Watch for the city-wide spike — usually triggered by one major chain raising prices — and fill up before it or wait for the next trough.
See Melbourne's current forecastBrisbane
Cycle length: 2–4 weeks
Best timing
Any day during the trough
Brisbane's cycle is shorter and faster than Sydney and Melbourne — roughly every 2 to 4 weeks. The upswings are sharp and the cycle less predictable, so checking the current cycle position is especially important. Prices can vary 10–20 cents per litre between trough and peak.
See Brisbane's current forecastPerth
Cycle length: Weekly (Monday reset)
Best timing
Tuesday to Wednesday
Perth is unique in Australia — WA FuelWatch resets at 6am every Tuesday morning, with prices set the day before and locked for 24 hours. This creates a predictable weekly pattern. Tuesday is typically the cheapest day as competition kicks in. The cycle is less about boom-bust and more about the weekly reset mechanism.
See Perth's current forecastAdelaide
Cycle length: 5–7 weeks
Best timing
Mid-week during trough
Adelaide has a visible cycle, though it's less sharp than Sydney or Melbourne. The trough tends to occur mid-week. Adelaide also responds to national market moves, so periods of high oil prices will push cycle troughs higher than usual — another reason to watch macro signals.
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.
PetrolCast's weekly market update flags both of these situations when they're active. The recommendation on your city's forecast page incorporates them automatically.