The South Australia state regulator fined six petrol stations nearly $20,000 for price breaches.
The watchdog ran checks and found problems mainly around charging standards.
Customers were urged to call in if they spotted excessive fees at pumps during the inspection.
No brand names or location details were released yet.
Total fines add up after ongoing patrol visits.
In Greater Western Sydney, Blacktown motorists now pay more for fuel than adjacent areas.
Regular pump checks reveal the area’s prices exceed other close competitors.
The price disparity means drivers there pay extra per litre each time they fill up.
The gap has expanded than what regulators anticipate in typical regional swings.