A number of service stations who had been expecting deliveries have already run dry.
According to a statement from Caltex Australia, the supply breakdown has been caused by "a disruption" to pipeline transfers from the Kurnell refinery in southern Sydney to terminals in Sydney and Newcastle.
Although Caltex says it hopes to restore the affected pipeline to normal operation over coming days, the shortages can be expected to extend well into next week.
The company says that affected areas in NSW include metropolitan Sydney, the Hunter region and the central coast, while supplies to the ACT are also affected.
Several service stations in these areas are now sitting on dry tanks of 95 and 98 octane premium unleaded.
Other regions are not affected at this stage, nor is regular 91 octane unleaded or E10 ethanol blended fuels.
However, Caltex says a very small number of sites may experience a shortage of regular unleaded and E10 as well, as a knock-on effect from the premium unleaded shortage.