Oil and gas products: pumped prices? It sounds like profit before people yet again! I need cheaper petrol. These comments were posted on Wednesday on the angry-sounding website PetrolPromise.com, which campaigns "for cheaper petrol and diesel." The European Commission has now waded in, launching a probe into possible "collusion" among oil producers to fix the prices of some oil and biofuel products. It has the potential to be the energy equivalent of the Libor banking scandal. But do not expect it to lead to cheaper petrol. Three oil companies involved - Shell, BP and Statoil - say they are co-operating with the investigation into whether there have been breaches of European antitrust rules in the setting of prices. The commission has teeth, as previous investigations show, including one into anti-competitive behaviour by Big Pharma to keep generic drugs off the market. And the Libor scandal suggests that regulators will come down hard on offenders. So far, three banks have paid $2.5bn in fines, with more almost certain to come. The commission can levy fines of up to 10 per cent of revenue for anti-competitive behaviour. Shell, BP and Statoil had combined 2012 revenue of nearly $1tn. So it is worth taking this probe seriously. But beware of too many parallels with Libor, which is an example of a cartel using inside information to set a price. The price of petrol is determined by factors including the price of a barrel of oil - one of the most traded and liquid products. That price used to be set by Opec but became market-based in the 1980s and is compiled by price reporting agencies such as Platts - also subject to the probe. The oil price has been high in the past few years and also exceedingly volatile. This may account for why petrol prices seem to move in only one direction. It would be good to know all the factors that determine the price of a litre of petrol. But it is unrealistic to expect it to be cheaper.