The South Australia state regulator fined six petrol stations nearly $20,000 for illegal pricing.
The monitoring team ran checks and found faults mainly around pricing rules.
Customers were urged to call in if they spotted price inflation at pumps during the sweep.
No brand names or addresses were released yet.
Total fines accumulate after recent patrol visits.
In Greater Western Sydney, Blacktown motorists now face higher for fuel than nearby suburbs.
Regular pump checks reveal the area’s prices exceed other nearby spots.
The difference means drivers there face higher costs per litre each time they fill up.
The gap has grown bigger than what regulators expect in usual regional swings.