I think that the fuel market became a lot less competitive after the supermarkets claimed half of the retail market. The prices used to be led by the independents. Now we have the supermarket outlets maintaining high prices and the independents trying to compete with them is a no win situation. If the supermarkets wanted to, they could drop their prices and send the independents out of business overnight, then claim the market for themselves.
Instead they have gone for the cosy option of maintaining high prices, just as they have done for groceries. Wholesale and retail margins are, as a result, at historically high levels. I have seen city fuel margins at 1-2 cents a litre during discount wars in the past. Now 10-14 cents a litre at the pump is the norm. 25 years ago, we had about 12,000 servos in Australia. How it's less than 6,000 and competition has suffered as a result.
Every year or two, we seem to have some kind of government inquiry into petrol prices. But none of them has yielded any benefit for the consumer. If you could run a car on bullShit, we'd all be traveling for free.