Fuel lines are rigid and flexible tubing conveying fuel from the fuel tank to the engine. They are routed throughout the vehicle’s chassis, including undercarriage and engine bay, and are constructed from materials compatible with gasoline, diesel, and ethanol blends – typically steel, nylon, or specialized polymers. Connections utilize quick-connect fittings, compression fittings, or flared ends to ensure leak-free operation under pressure. Modern fuel lines often incorporate protective sleeves or coatings to resist abrasion, heat, and chemical exposure. Failure modes include corrosion, cracking due to age/heat cycling, and leakage at connection points.