The best oil to use in a Zippo lighter is Zippo lighter fluid. This specialized fuel is designed to provide a consistent flame for the lighter, ensuring reliable ignition and a long-lasting burn. Zippo lighter fluid is a highly volatile, flammable liquid that is specifically formulated to work with the Zippo lighter's design, which includes a wick and a fuel reservoir.

The reason Zippo lighter fluid is the preferred choice is due to its high volatility, which allows it to vaporize quickly and efficiently. This rapid vaporization ensures that the flame is sustained and that the lighter can be easily re-ignited. Additionally, Zippo lighter fluid is formulated to be safe for use with the Zippo lighter's materials, preventing damage to the lighter's internal components.

According to a study by the Zippo Manufacturing Company, Zippo lighter fluid is the only fuel that has been tested and approved for use in Zippo lighters. The company has conducted extensive testing to ensure that the lighter fluid is safe and effective. The study also found that using other types of oil, such as gasoline or kerosene, can damage the lighter's internal components and lead to unsafe conditions. Therefore, using Zippo lighter fluid is not only the most effective choice but also the safest for the user and the lighter itself.