Speaking from an upstream oil company (no petrol stations) the price of oil depends on a lot of factors. The demand, the amount produced etc. If all companies produced a shed load of oil the price would go down, and on the other hand if the demand goes up compared to that being produced the price rises.
Also solely blaming oil comapnies for putting prices up is a little bit wrong really… the price to take a barrel of oil out of the ground is going up and it ain’t cheap to find new oil either!!
I don’t know what the price fixing entails if its solely just the petrol station side but in reality the price a barell of oil comes in at is a lot lower than it was a few years ago.