What is the most common fuel oil utilized in boilers?

The most common fuel oil utilized in boilers is indeed #2 fuel oil. This type of oil is widely used due to its balance of cost, availability, and efficiency. #2 fuel oil is a refined product that provides good combustion characteristics, making it suitable for residential, commercial, and industrial heating applications. It is particularly favored in the context of boiler operations because of its relatively low viscosity, which allows for easier handling and better atomization during the combustion process.

Other options, while also usable in specific scenarios, are less common. For instance, #1 fuel oil is lighter and primarily used in colder climates due to its lower viscosity, but it doesn't provide the same level of energy density or efficiency in larger-scale boiler applications. #4 and #5 fuel oils are heavier and typically used in industrial applications where high fuel consumption is required, but their use is more niche and not as prevalent in standard boiler operations compared to #2. The widespread infrastructure and availability of #2 fuel oil further reinforce its status as the most commonly employed fuel in boiler systems.