Flat engines, also known as horizontally opposed engines, are a type of internal combustion engine where the cylinders are arranged in two horizontal rows on either side of a central crankshaft. This design allows for a lower center of gravity, which can improve vehicle stability and handling. A well-known example of a flat engine is the Subaru Boxer engine, commonly used in Subaru vehicles. One of the main advantages of flat engines is their smooth operation. Because the opposing cylinders balance each other out, they produce less vibration compared to traditional inline or V-shaped engines. This results in a more comfortable driving experience, making flat engines popular in performance cars and aircraft as well.