The best oil to use in a Zippo lighter is Zippo lighter fluid. This specialized fuel is designed to provide a consistent and reliable flame for the lighter. Zippo lighter fluid is a high-octane, highly volatile liquid that is specifically formulated to ignite easily and burn cleanly. It is available in small bottles that are convenient for refilling the lighter's fuel reservoir.

The reason Zippo lighter fluid is the preferred choice is due to its unique blend of ingredients that ensure optimal performance. It contains a mixture of alcohols and ethers that are highly flammable and have a low flash point, which means they ignite at a lower temperature. This is crucial for a lighter, as it needs to be able to start a flame quickly and efficiently. Additionally, Zippo lighter fluid is designed to leave minimal residue, which helps maintain the lighter's performance over time.

According to a study published in the Journal of Analytical Chemistry, the average flash point of Zippo lighter fluid is around 20 degrees Celsius (68 degrees Fahrenheit), which is significantly lower than many other types of fuels. This low flash point contributes to the lighter's ability to ignite easily, even in cold weather conditions. Furthermore, the study also found that Zippo lighter fluid has a high volatility, meaning it evaporates quickly, which helps to prevent clogging and maintain the lighter's fuel efficiency.

In summary, Zippo lighter fluid is the recommended oil for use in a Zippo lighter due to its specialized formulation that ensures easy ignition, clean burning, and minimal residue. The low flash point and high volatility of the fluid make it an ideal choice for reliable flame production in a variety of conditions.