Mandurah, want to save more than $500 a year on petrol? Here’s how...

Perth motorists who buy petrol at the low point of the regular price cycle can save up to $520 per year, a new ACCC report has revealed.

The report found it has become easier in Perth to pick the "trough" and "peak" days of price cycles, while it is getting harder to do so in the eastern states.

Price cycles involve sudden increases in petrol prices, usually led by one or more retail sites. The decline back to lower price levels is slower than the increase.

“While they are not illegal, the retailers’ use of price cycles to maximise profits really infuriates drivers as they can see no reason for them to exist,” ACCC Commissioner Mick Keogh said.

“It’s not uncommon for drivers to notice prices jumping 20 cents or more in a very short period of time, and the price you see being charged on the way to work can be very different to the one on the way home.”

A regular price cycle began to develop in Perth in 2009 and in 2016 the cycle was "extremely predictable", with Monday the cheapest day and Tuesday most expensive.

The report found changes in price cycles between 2009 and 2016 cost motorists in the eastern states but benefited Perth drivers. The FuelWatch scheme benefited motorists in WA.

Related content:

The 2017-18 estimated total savings in Perth if all motorists that filled up weekly bought petrol at the trough price rather than the peak price would be around $210 million a year.

The volume of petrol sold is influenced by the price and the report estimated the financial impact on consumers of price cycles by comparing the average price with the average volume-weighted price across each cycle.

The increased difference between the average price and average volume-weighted price in Perth saved motorists between $15 million and $20 million in 2016.

Mr Keogh advised motorists not to wait until their tank was empty to buy petrol and take advantage of the price cycle's predictability.

“Favouring the best-priced retailers sends a clear signal to petrol stations about what they need to do to get your business," he said.

"The more people who do this means the more pressure there is on retailers to compete aggressively on price."

If drivers noticed prices going up at one retailer, they could use an app to find another which hasn’t yet raised its price.

"For drivers who don’t use their cars that often, or drive as far, it is possible to time purchases at the low point of the cycle and pay below what it costs retailers," Mr Keogh said.

The estimated yearly savings made by buying at the low point of the cycle are around $175 in Sydney, $150 in Melbourne and Brisbane, and $200 in Adelaide.