What does viscosity of fuel oil measure?

Viscosity of fuel oil measures the internal resistance to flow, which is a critical property in various applications involving fluid dynamics. In the context of fuel oils, viscosity indicates how thick or thin the oil is. A higher viscosity means the oil is thicker and flows more slowly, while a lower viscosity indicates that the oil is thinner and flows more easily.

Understanding viscosity is essential for the proper handling and utilization of fuel oils, as it affects pumping, atomization in burners, and overall combustion efficiency. For instance, if the fuel is too viscous, it may not flow freely through pipes or be effectively atomized for combustion, leading to poor performance or operational issues.

The other choices, while related to fuel oils, do not accurately define viscosity. Temperature stability assesses the consistency of a liquid's properties over a range of temperatures, density relates to mass per unit volume, and flash point is the lowest temperature at which the fuel can vaporize to form an ignitable mixture. These properties are important but do not pertain directly to how easily fuel oil flows, which is what viscosity measures.