Monday is the new cheap day for Perth petrol

• New weekly price cycle sees cheap day on Mondays

• Mount Lawley, South Lake and Roleystone among cheapest suburbs for fuel 

Perth's new weekly petrol price cycle has seen Monday become the new cheap day for motorists to buy petrol, with most retailers now hiking their prices on a Tuesday.

Commerce Minister Michael Mischin said an analysis of price trends by FuelWatch in recent weeks has discovered a new pricing pattern by the major petrol retailers.

Mr Mischin said the analysis showed that Coles Express Mount Lawley was consistently the cheapest site for unleaded petrol in Perth since the beginning of this year.  The cheapest site in the south was Caltex Woolworths South Lake and Better Choice Roleystone was the cheapest in the east.

"Until recently and for about five years, Perth had a predictable weekly price cycle where, on average, Wednesday was the cheapest day of the week to buy petrol and prices rose dramatically on a Thursday," he said.

"However at the end of May, most Caltex service stations suddenly broke that pattern and began to increase their prices earlier in the week, making the traditional cheap days the most expensive.  Other major fuel companies followed that lead.

"It appears that this new cycle has been established for several weeks now and we need to advise motorists to fill up on Mondays to take advantage of the new weekly price cycle.

"On any day, prices can vary widely from site to site and from brand to brand.  The difference between the cheapest and most expensive has been up to 27 cents per litre, which is a $16 price difference for an average tank of petrol."

The Minister said the FuelWatch system was unique to Western Australia and prices on the website were locked in for a 24-hour period from 6am, giving consumers certainty and transparency when making their purchasing decisions.

"I encourage motorists to use the services of FuelWatch to locate the cheapest fuel outlet nearest to them and reward them with your business," Mr Mischin said.

"After 2.30pm each day, motorists can also check the following day's prices and decide when the best time is to fill up.

"Almost 38,000 people have already signed up with a surge of 1,000 new subscribers joining last month.  The FuelWatch website gets more than half a million visits every month and that has been increasing."

Fact File

• FuelWatch was created by the Western Australian Government in January 2001 to monitor the daily prices for petrol, diesel and LPG/Autogas within metropolitan Perth and regional areas from Albany to Geraldton

• The FuelWatch website received a record number of 691,288 visits in June 2015, which is 38% higher than the previous record of 500,874 in January 2015 and a jump of more than 45% from May to June.  This can be attributed to the fuel cycle disruption causing added media attention and confusion among motorists

• Motorists can check fuel prices and subscribe to email alerts at http://www.fuelwatch.wa.gov.au or call 1300 30 40 54 

Minister's office - 6552 5600

Top 10 cheapest unleaded fuel sites in Perth to June 30, 2015: