The best oil to add in a Zippo lighter is a high-quality lighter fluid, specifically designed for Zippo lighters. This fluid is typically a blend of naphtha and isoparaffin, which provides a clean burn and ensures the lighter operates efficiently. The use of specialized lighter fluid is crucial because it is formulated to have the right viscosity and volatility for optimal performance in Zippo's unique design.

The reason for using a specific lighter fluid is due to the lighter's internal components and the way it operates. Zippo lighters have a wick system that requires a fuel with the right balance of volatility and viscosity. If the wrong type of oil is used, it can lead to inefficient burning, clogging of the wick, or even damage to the lighter itself. According to a study by the Zippo Manufacturing Company, the recommended lighter fluid has a flash point of around 100°F (38°C) and a pour point of -40°F (-40°C), ensuring it vaporizes easily at room temperature but remains liquid in cold conditions.

Using a non-compatible oil, such as kerosene or gasoline, can cause several issues. Kerosene has a higher flash point and pour point, making it too thick and volatile for the Zippo lighter's wick system. Gasoline, on the other hand, has a lower flash point and can be too flammable, leading to a risk of fire or explosion. Moreover, gasoline has a strong odor and can leave a residue on the lighter, affecting its performance and appearance.

In summary, using the correct lighter fluid is essential for the proper functioning and longevity of a Zippo lighter. The specialized fluid ensures a clean burn, prevents damage to the lighter, and maintains the integrity of the wick system.