Fuel filters are inline filters installed within the vehicle’s fuel lines, typically near the fuel tank or engine. They mechanically remove particulate contaminants—such as dirt, rust, and scale—from fuel before it reaches the engine. Filtration ratings are measured in microns, with lower numbers indicating finer filtration. Modern filters utilize pleated paper, synthetic fiber, or ceramic elements to maximize surface area and flow rate. Materials must be compatible with gasoline, diesel, and ethanol-blended fuels, and housings are constructed of metal or durable polymers to withstand fuel pressure.