* Intended Use: Number 2 diesel is specifically formulated for use in diesel engines, while fuel oil (specifically #2 fuel oil, which is the most common type) is primarily used for heating purposes in furnaces and boilers. While some older, heavier-duty diesel engines *might* run on #2 fuel oil, it's not recommended due to potential performance issues and increased maintenance.
* Cetane Number: Diesel fuel (Number 2) has a higher cetane number than #2 fuel oil. Cetane number measures the ignition quality of diesel fuel – a higher number means easier and quicker ignition, leading to smoother combustion and better engine performance.
* Sulfur Content: ULSD (Number 2 diesel) has a much lower sulfur content than #2 fuel oil. This lower sulfur content is crucial for meeting emission standards and protecting engine components from corrosion and wear. The high sulfur content in fuel oil contributes to air pollution and engine problems if used in diesel engines.
* Additives: Diesel fuel contains various additives designed to improve performance, lubricity (reducing wear on engine parts), and to help prevent fuel-related problems. #2 fuel oil may contain fewer or different additives, tailored for heating applications.
* Viscosity: While there can be some overlap, diesel fuel generally has a lower viscosity (flows more easily) than #2 fuel oil, which is designed to atomize effectively in a diesel engine's combustion chamber.
In short: While there might be some similarities in their chemical makeup, Number 2 diesel is a refined fuel optimized for use in diesel engines, while #2 fuel oil is designed for heating and is generally not suitable for use in modern diesel engines. Using #2 fuel oil in a diesel engine can cause serious damage.
