Why Do Petrol Prices Change Every Day in Australia?
How Australian fuel prices are set, why they go up and down, and when the best time to fill up is. A plain-English guide to the petrol price cycle.
If you've ever filled up on Monday at $1.75 and driven past the same station on Wednesday showing $1.95, you're not imagining things. Australian petrol prices really do change that much, that fast. Here's why.
Key takeaway: Petrol prices are set by a chain that starts in Singapore, passes through wholesalers, and ends with local competition between servos. The price cycle is real, and checking prices before filling up is the single easiest way to save.
It starts in Singapore, not Australia
Australia imports most of its refined fuel. The benchmark price for our region is Platts Singapore Mogas 95 — the wholesale price of unleaded petrol in Singapore, published daily by S&P Global Platts.
When that benchmark goes up — because of crude oil prices, refinery issues, or global conflict affecting supply — the wholesale cost of fuel in Australia follows within days.
The wholesale-to-bowser chain
The price you see at the pump is built from several layers:
- Singapore benchmark — the international wholesale price
- Shipping and insurance — getting it to Australian terminals
- Terminal Gate Price (TGP) — what fuel companies charge retailers at the depot gate. Required to be published daily by wholesalers under the Oilcode (overseen by the ACCC).
- Retailer margin — the profit the servo makes on each litre
- Taxes — fuel excise (currently ~53c/L) and 10% GST
Steps 1–3 change based on global markets and the AUD/USD exchange rate. Step 4 is where the day-to-day swings come from.
The price cycle
In capital cities like Brisbane, Sydney, and Adelaide, petrol prices follow a regular cycle — typically rising sharply over a day or two, then slowly dropping over the next week or so. This is driven by retailers:
- At the bottom of the cycle, one or two big chains raise their prices. Others follow quickly — nobody wants to sell at a loss.
- At the top, competition kicks in. Stations start undercutting each other, and prices drift down day by day until the next reset.
The length of the cycle varies. In recent years, Brisbane, Sydney, and Melbourne have all seen cycles averaging 4–7 weeks — much longer than the 1–2 week cycles of a decade ago. Regional towns often don't follow a cycle at all — prices change less often but can stay high for weeks.
So when should I fill up?
The best time to fill up is at the bottom of the cycle, just before prices jump. The tricky part is knowing when that is.
That's where a live fuel price tool helps. Rather than trying to predict the cycle, you can just check what prices are right now in your area. If prices near you are low compared to the recent average, it's a good time to fill up. If they've just spiked, it might be worth waiting a day or two — or driving to a suburb that hasn't risen yet.
For more ways to time your fill-ups and cut costs, see our guide to 10 practical ways to save on fuel.
Why prices differ between suburbs
Even within the same city, prices can vary by 20 cents per litre or more. This comes down to:
- Competition — areas with lots of servos tend to be cheaper
- Demographics — some retailers charge more where they think customers are less price-sensitive
- Costs — rent, wages, and delivery costs vary by location
- Brand strategy — independent servos often undercut big chains, but not always
The bottom line
Petrol prices change daily because they're linked to a global commodity that moves constantly, filtered through a competitive retail market where stations are constantly adjusting to each other. The cycle is real, the savings are real, and checking prices before you fill up is the single easiest way to pay less.