When I was in the Sippy Downs area (roughly 1.5 hours north of Brisbane) a year ago (Got to meet Coulomb and pals
), prices would rise and fall in a predictable weekly cycle with the cheapest being available on Wednsday right around the time the tanker truck rolled in to refill the station. Needless to say, there was always a line up.
The cycle here in Brisbane is a little more chaotic now. If it does the weekly cycle (some weeks it doesn't now), it peaks later, around Friday midday.
I don't think it was ever tied to deliveries; the petrol retailers would fax their suppliers and say "Hey, Joe down the road has posted $1.39 per litre, I need to match that price to stay alive!". The supplier would fax back what the new price is. Somehow they established an "average" price for the retailer to pay.
When challenged about the price rises at the end of the cycle, the suppliers would always claim that the highest price is the "real" price, and the lower prices were all discounts. They had to stop the discounts when they got to a certain point, since they claim to be losing money there.
Needless to say, the petrol companies are often being investigated for collusion by the ACCC (Australian Competition and Consumer Commission, a government sponsored "independent" body), but they rarely seem to get fined for it. It's almost comical.
I guess what it means is that the poorer people have to queue up at the cheaper times of the week, and the richer people pay more but wait less at the other times. Capitalism at its most insane, I say. It can only happen (as bad as this) with fuel, since you can't legally store it except in your vehicle's limited size tank.
They've actually gone to LED price signs at some petrol stations now; it saves all that climbing up a ladder to change the prices so regularly.
Recently, the petrol prices are increasingly controlled by two grocery retailers (Woolworths and Coles). They have been buying up petrol retailers that have been going to the wall due to the low margins, and selling petrol at Grocery branded outlets. If you shop more than a certain amount, you get 4c per litre (occasionally more) off the price of petrol.
Back when the price of petrol was 60c a litre, that was a good deal. Now, with prices over twice that, they haven't increased the incentive, but apparently enough people use the discount dockets to make it worthwhile.
Just a week or two ago, Coles reduced the price of 3L of milk from ~$3.40 to $3.00, and the very same day, petrol shot up to ~ $1.43 per litre from about $1.26. There are some that suggest that the two price changes were related!
(I'm one of them.)
So now milk is being subsidised by petrol, and petrol is being subsidised (a little) by other groceries. Lunacy.
Meanwhile, recent floods and a cyclone have dramatically put up the price of fruit and vegetables. Some would say that this is connected with the continued use of too-cheap petroleum. I'd better stop there to stop a flame fest.