All the major oil companies have now dropped their petrol and diesel prices following Shell's lead this morning.
From today 91 and 95 octane petrol and diesel will cost 4c a litre less.
Petrol prices now are 91 octane 139.9c a litre, 95 octane 144.9c and diesel 116.9c.
Since July 17, petrol has dropped a total of 79c a litre, while diesel has dropped 69c a litre since July 8.
A Shell spokesman said the price drop was due to the continued decrease in the cost of refined product.
The price for a barrel of oil plunged below $US44 overnight, the lowest level for almost four years.