If you fill up in Sydney, you’ve probably noticed something odd. Petrol prices jump up fast, then slide back down slowly, over and over. This is called the petrol price cycle.

What the cycle looks like

The pattern has two phases:

  • A sharp rise. One retailer raises its price. Others follow within a day or two. The average price across the city jumps.
  • A slow fall. Retailers cut prices bit by bit to win customers back from each other. This takes much longer than the rise.

Then the cycle repeats.

The Australian Competition and Consumer Commission (ACCC) tracks this pattern in Sydney and Australia’s four other largest cities. In 2025, the ACCC found Sydney’s average cycle lasted about five weeks. Cycle length isn’t fixed. The ACCC has tracked it growing longer in Sydney, Melbourne, and Brisbane: about four weeks in 2018, about seven weeks by 2023. That’s why we describe it as roughly four to seven weeks, not a fixed number.

Why the cycle exists

The ACCC says the cycle comes from pricing decisions retailers make, not from changes in the wholesale cost of fuel. Retailers raise prices together, then compete on price to win customers back, until margins get thin and someone raises prices again to reset the cycle.

Not every retailer takes part. Independent stations and supermarket-linked chains often price differently from the big retailers. That’s part of why prices vary so much between petrol stations on the same day.

How to read it

One number matters most if you want to use the cycle: how long it takes prices to climb from low to high.

In Sydney, the ACCC says average prices can take up to two weeks to move from their low point to their high point. That gives you a window to notice the rise starting and buy before it finishes.

The Sydney petrol price cycle: sharp rise, slow fall, repeating roughly every five weeks Sharp rise: up to 2 weeks Slow fall: about 3 weeks cheapest window
Sydney's cycle rises sharply over up to two weeks, then falls slowly for about three, repeating roughly every five weeks; the cheapest window sits at the bottom, just before the next rise.

The ACCC’s most-cited savings estimate is older. In a 2018 analysis, the ACCC looked at buying at the cycle’s low point instead of paying the average price. It found that could save a Sydney driver around $175 a year.

A later ACCC analysis, covering 2023, found a different figure: around $407 a year in Sydney. That number combines two things: buying at the cycle’s low point, and comparing prices across stations. It isn’t the same measure as the 2018 figure, so the two aren’t directly comparable.

What can break the pattern

Price cycles are a pattern of retailer behaviour, not a fixed law. They can pause or disappear during periods of unusual volatility in global oil prices, such as a war or a major supply disruption. When that happens, prices can stay high, or move without a clear pattern, until conditions settle.

Where these numbers come from

We don’t run our own long-term price study. The cycle length and savings figures above come from the ACCC’s public reporting on petrol price cycles in Australia’s five largest cities. Check the sources below for the latest figures, since cycle length changes from year to year.

Sources:

Next, read Best day to fill up for how to time a purchase against this pattern in practice.