What type of fuel do oil furnaces typically burn?

Oil furnaces primarily burn #2 fuel oil, which is a specific type of fuel commonly used for residential heating. This type of oil is favored because of its relatively high energy content and easy availability, making it cost-effective for heating applications. #2 fuel oil is processed to meet certain specifications that allow it to be burned cleanly and efficiently in oil furnaces.

While #1 fuel oil and diesel are types of oil, they are not typically used in residential oil furnaces due to their different characteristics and applications. Natural gas is also a common heating fuel but is not relevant to oil furnaces as they specifically utilize oil-based fuels. Thus, the focus on #2 fuel oil as the correct answer highlights its suitability and common usage in oil heating systems.