Oil companies dropped the domestic retail price of petrol by 4 cents per litre on Monday.
The price also fell 4 cents on Thursday, mainly due to a fall in the price of US crude oil.
New York's main oil contract, light sweet crude for August delivery, closed at $US128.88 a barrel on Friday after falling by more than $US15 since Tuesday.
In London, Brent North Sea oil for September delivery was at $US130.19.
Shell, BP, Caltex and Mobil all lowered the price of 91 octane by 4 cents to $2.10.9 per litre on Monday.
However, the price of diesel remains unchanged.
The Automobile Association says it's too early to say whether it means prices are begining to stabilise.
