MODEL RELEASED. Diesel fuel station. Car driver filling the fuel tank of his car with diesel from a fuel station pump. Diesel, like petrol, is a fossil fuel obtained from oil. Diesel is denser than petrol, and releases more energy when burnt. It can only be used in diesel engines, and not in petrol engines, as seen on the warning sign (lower centre). Diesel used to be cheaper than petrol, but as of 2006 the price is now close to that of petrol. Here, at a fuel station on the island of Islay, Scotland, the price is 109.9 pence per litre. Islay is in the Southern Hebrides, off the West Coast of Scotland.