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 highly volatile, flammable liquid that is specifically formulated to ignite easily and burn cleanly. It is available in various sizes and is widely available at most convenience stores and tobacco shops.

The reason Zippo lighter fluid is the preferred choice is due to its high volatility, which allows it to ignite quickly and maintain a stable flame. The fluid is also designed to be safe for use in Zippo lighters, as it does not damage the internal components or cause rust. According to a study by the Zippo Manufacturing Company, Zippo lighter fluid is the only fuel that is recommended for use in Zippo lighters, as it ensures optimal performance and longevity of the lighter. Additionally, using the correct fuel helps prevent the buildup of residue that can lead to clogs and malfunctions.