South Australian drivers will be worse off when shopping for discount petrol because of a deal between fuel retailers and the Australian Competition and Consumer Commission (ACCC), the RAA says.

Spokesman Mark Borlace said, until today, the RAA received twice-daily information on which petrol stations had the cheapest fuel.

The RAA then published the information on its website.

But the association said that service was no longer available because of an arrangement between fuel businesses and the ACCC.

Instead, the association can only provide average Adelaide petrol prices once per day.

"If you pull up a service station, even though you might know the average, you won't know whether the service stations around you are cheaper," Mr Borlace said.

He said the difference between the highest and lowest prices could sometimes be as much as 40 cents per litre.

"The savings people that might be missing out on because they can't see this data could be between $12 and $24 per [60-litre] tank over the past year."

He said the State Government should legislate to enforce price-monitoring arrangements like those in place in New South Wales.

"They have mandated so that every fuel retailer has to supply to a government database real-time fuel pricing so that the public can actually have that data from every retailer," Mr Borlace said.

"What we've done is we've approached the Attorney-General [John Rau] to say we think that should happen here."

In a statement, Mr Rau said the Government would consider change "if there is compelling evidence of market failure".

"The ACCC reports that a number of apps already exist giving consumers real-time fuel prices," he said.

"Introducing another app, like the NSW Fuel Check, would be at a cost to SA taxpayers to administer and create extra red tape for service station operators."