The oil crisis has not only caused petrol prices to soar, it has revealed just how little competition there is among the big oil companies. A couple weeks ago the ACCC announced that it would be looking into uncompetitive behaviour by petrol companies in the rural areas.
The article shows how petrol price rises have been affected in different parts of Australia.
https://thepoint.com.au/news/260327-petrol-prices-are-soaring-in-sync-collusion-or-coincidence
This was the case in Melbourne too, when I was working at a service station back in my Uni days.
Not sure when things changed, but apparently it moved to a fortnightly cycle at some point, before completely losing any semblance of predictability post-COVID.