What is a common indicator of poor combustion in an oil furnace?

A common indicator of poor combustion in an oil furnace is visible soot buildup. When combustion is not occurring efficiently, it can lead to the incomplete burning of fuel. This incomplete combustion produces carbon byproducts, which manifest as soot. The presence of soot indicates that the furnace is not burning oil cleanly, resulting in inefficiencies and potential damage to the system.

Furthermore, soot can accumulate on heat exchangers and other internal components, leading to reduced efficiency, overheating, and even operational failures if left unaddressed. Regular maintenance and monitoring for soot accumulation are crucial for ensuring the burner operates effectively and safely.

While other factors like excessive noise or frequent shutdowns may also suggest issues with the furnace, they do not specifically indicate problems related to the combustion process as directly as soot buildup does.