Which type of smoke is typically associated with burning a mixture of fuel and oil?

Black smoke is typically associated with the burning of a mixture of fuel and oil. When fuel and oil combust together, particularly in an engine, the incomplete combustion of the fuel results in soot and other particulate matter being released, which can create a dark, opaque smoke. This is often indicative of a rich fuel mixture, where there is more fuel than the engine can completely burn, leading to the emissions of larger carbon particles.

In contrast, other types of smoke can indicate different issues. Blue smoke generally signifies that oil is burning in the combustion chamber, which can occur due to worn piston rings or valve seals. White smoke often points to coolant entering the combustion chamber, usually due to a blown head gasket, and gray smoke can arise from burning transmission fluid or other engine malfunctions. Each type of smoke provides diagnostic clues about the engine's condition and the nature of its combustion processes.