Which type of oil is used in boiler?

The type of oil commonly used in boilers is fuel oil, specifically No. 2 heating oil, which is a light distillate oil suitable for residential and commercial heating. In industrial applications, heavier oils like No. 6 fuel oil may be used. Additionally, biofuels and waste oils are increasingly being explored as alternative fuels for boilers to improve sustainability. Always ensure that the oil type is compatible with the specific boiler system.