The most commonly used oil for fuel heating stoves in the United States is 1 heating oil. This type of oil is designed for high-efficiency, low-temperature combustion, making it ideal for heating systems in residential and commercial buildings. 1 heating oil has a lower viscosity than other types of heating oil, which allows it to burn more cleanly and efficiently. According to the U.S. Energy Information Administration (EIA), 1 heating oil has a higher energy content per gallon compared to other types of heating oil, such as 2 heating oil or kerosene, which means it provides more heat for less fuel. Additionally, 1 heating oil is less likely to cause soot buildup in the stove, which can improve the longevity and performance of the heating system.