Filling up your vehicle can be an expensive business, but does it need to cost quite as much as it does? Prices have fallen since the record highs seen immediately after Russia’s invasion of Ukraine, but many experts believe the price per litre should have fallen further.In this week’s Which? Investigates we take a look at the factors propping up forecourt prices, hearing how the price of wholesale oil doesn’t reflect what we’re currently seeing, and asking whether retailers are looking to make money while they can before a ban on new petrol and diesel cars comes into force.Check out our annual fuel cost calculator and sign up to our free weekly newsletters.