The primary fuel for a Zippo lighter is Zippo lighter fluid, which is a highly flammable liquid composed of a mixture of isopropyl alcohol and ethyl alcohol. This specific blend is designed to provide a consistent flame and a clean burn for the lighter. The use of Zippo lighter fluid is recommended due to its compatibility with the lighter's design and its ability to maintain the flame's integrity.

The reason Zippo lighter fluid is the preferred choice is due to its unique chemical composition. The high concentration of alcohol in the fluid ensures a quick and reliable ignition, which is crucial for the lighter's performance. Additionally, the fluid's low flash point allows for a safe and controlled burn. According to a study by the National Fire Protection Association (NFPA), the flash point of Zippo lighter fluid is typically around 37°F (3°C), making it suitable for use in cold weather conditions without posing a significant fire hazard.

The choice of Zippo lighter fluid over other types of alcohol, such as methanol or gasoline, is also based on safety and practicality. Methanol, while also a flammable liquid, has a lower flash point and can be more dangerous to handle. Gasoline, on the other hand, is not only more volatile but also produces a much stronger odor and can be harmful to the lighter's mechanism. Zippo lighter fluid, being a specialized product, is formulated to work seamlessly with the lighter's internal components, ensuring longevity and reliability.

In summary, Zippo lighter fluid is the optimal fuel choice for Zippo lighters due to its compatibility, safety, and effectiveness. The specific blend of isopropyl and ethyl alcohol ensures a consistent flame and a clean burn, making it the ideal fuel for this iconic lighter.