The AA's predicting a dramatic cut to premium petrol prices

Some service stations are charging up to 40 cents extra per litre for 95 and 98 octane fuel, compared to 91.

The AA's Mark Stockdale says in many cases it's because service stations aren't advertising their price.

But he says after a request from Commerce and Consumer Affairs Minister Kris Faafoi, companies should start to display all petrol costs, not just 91.

He says premium petrol costs should drop to under 10 cents per litre.