The South Australia government agency fined six petrol stations nearly $20,000 for pricing violations.
The inspectorate ran checks and found problems mainly around charging standards.
Customers were encouraged 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 latest patrol visits.
In Greater Western Sydney, Blacktown motorists now pay more for fuel than nearby suburbs.
Regular pump checks show the area’s prices sit above other nearby spots.
The difference means drivers there face higher costs per litre each time they fill up.
The gap has expanded than what regulators expect in usual regional swings.