Diesel fuel is a liquid fuel specifically engineered for compression-ignition engines, primarily derived from petroleum distillates but increasingly from alternatives like biodiesel, biomass-to-liquid (BTL), and gas-to-liquid (GTL) processes. The technology traces back to German scientist Rudolf Diesel, who invented the engine around 1892 and initially tested a wide range of fuels—including kerosene, crude oil, and even peanut oil—before the modern petroleum-based standard was adopted. Today, diesel is heavily standardized, such as under EN 590 in the EU, and since 2016, nearly all road fuel in the UK, Europe, and North America is ultra-low-sulfur diesel (ULSD), a reformulation that dramatically reduces harmful sulfur emissions. Known by regional names like DERV in the UK, distillate in Australia, and Solar in Indonesia, it remains the dominant power source for heavy trucks and is also used in some non-diesel engines, although older engines produce exhaust with significant health risks. As a high-volume refinery product, diesel continues to evolve, with cleaner alternatives like biodiesel and synthetic fuels being adopted to meet rising environmental standards.