University of New South Wales associate professor Frank Zumbo said Sale residents were "being ripped off by upwards of seven cents per litre'' because oil companies had not been passing on recent cuts in the wholesale price of unleaded fuel.

A member of the Trade Practices Committee of the Law Council of Australia and government adviser on competition and fair trading, Prof Zumbo points the finger at oil companies.

"You may have noticed that the average prices have stubbornly stayed around $1.23 to $1.24 per litre during the past five weeks.

"However, during the past five weeks the average terminal gate price (that is, the wholesale price for unleaded) has fallen by about seven cents per litre.''

Sale petrol stations, along with Traralgon, Morwell and Moe, recently recorded seven-day rolling average unleaded fuel prices above 120 cents per litre, while Bairnsdale recorded a price of 119 cents per litre.

The lowest prices were recorded at Warrnambool (111.5 cents per litre) and Geelong (110.7 cents per litre).

Prof Zumbo believes a lack of competition around Sale is the cause of the price discrepancies.

"I was looking at Google Maps, and I saw this cluster of higher petrol prices in Sale,'' he said.

"The only explanation is that oil companies aren't passing on the price cuts (to Sale).

"In terms of Geelong, there is a 12 cent gap.

"There's no explanation other than oil companies playing games in Sale.''

Prof Zumbo said this reflected a lack of competition and as such, should be investigated by Australian Competition and Consumer Commission petrol commissioner Joe Dimasi.

But GPG Mobil owner Anthony Van Brugel said Prof Zumbo's claims of Sale being "ripped off'' were unfounded.

Mr Van Brugel said the majority of petrol stations in Sale were independently owned, and oil companies had little direct influence on fuel prices.

"Mobil doesn't operate my stations - I do,'' he said. "No oil companies are playing games in Sale because they're all independently owned (with a few exceptions).''