The oil in a Zippo lighter is a highly refined kerosene-based fuel. This type of oil is specifically chosen for its volatility, which allows it to ignite quickly and efficiently when the lighter's flint wheel strikes the flint. The oil is stored in a small reservoir within the lighter and is released through a wick when the lighter is opened, ensuring a steady flame for lighting cigarettes or other items.

The choice of kerosene-based oil for Zippo lighters is due to several factors. Firstly, kerosene has a high flash point, meaning it can ignite at a relatively low temperature, making it ideal for a quick and reliable flame. Secondly, kerosene is less likely to evaporate compared to other types of fuel, ensuring a longer-lasting flame. According to a study by the National Fire Protection Association (NFPA), kerosene has a flash point of approximately 100-140 degrees Fahrenheit, which is well-suited for the demands of a lighter.

Additionally, the use of kerosene in Zippo lighters is advantageous because it is less flammable than gasoline, reducing the risk of accidental fires. The NFPA also reports that kerosene has a lower vapor pressure than gasoline, which means it is less likely to form explosive mixtures in the air. This safety aspect is crucial for a product designed for everyday use.

Furthermore, kerosene's ability to burn cleanly without leaving residue on the lighter's exterior is another reason for its preference in Zippo lighters. This clean burn is beneficial for maintaining the lighter's appearance and ensuring that it can be used for an extended period without the need for frequent cleaning.

In conclusion, the oil in a Zippo lighter is a kerosene-based fuel due to its volatility, high flash point, lower flammability, and clean burn characteristics. These properties make it an ideal choice for a reliable and safe lighter that can be used for various applications.