Petrol is on track to fall to its lowest price since early June as the stronger Australian dollar and lower global oil prices bring relief for motorists.
Australian Institute of Petroleum figures show that the average price in Perth last week fell by half a cent to 145.9ï¿½ a litre.
Prices ranged between 141.5ï¿½ and 150.5ï¿½ a litre through the week.
It is the lowest average price in 20 weeks for Perth. It peaked at $1.55ï¿½ a litre in late July. Perth prices could fall further in coming weeks if trends in other major capital cities are replicated locally.
Sydney's average price dropped 5.3ï¿½ last week to 143.4ï¿½ a litre, while in Melbourne they tumbled 6.2ï¿½ to 140.7ï¿½ a litre.
Perth's average price now stands above the national average. Traditionally it has been slightly lower than the national average.
CommSec chief equities economist Craig James said prices across the country were likely to fall in the coming days by up to 3Â¢ a litre.
Mr James said motorists were benefiting from two critical developments.
"World oil prices have eased in large part because markets are well supplied with oil given the absence of production disruptions or geopolitical concerns," he said.
"And the Aussie dollar has lifted over the past fortnight on the perception that the US Federal Reserve will wind back stimulus only slowly in the months ahead."
Since early last month, the average price in Perth for unleaded petrol has dropped 6Â¢ a litre.
Nationally, prices have come down by more.
The drop has increased the spending power of motorists about $4.50 a week.
Mr James said if prices continued to fall it would be a boost to the retail sector.
"Retailers have reason to celebrate the falling petrol price, especially as it comes at a time of more stable financial markets and gains in home prices and share prices," he said.