What is the black smoke that comes out of cars called?

The black smoke that comes out of cars is typically referred to as "soot" or "diesel smoke." It is often a sign of incomplete combustion, which can occur in diesel engines due to factors like poor fuel quality, clogged filters, or malfunctioning injectors. This type of smoke can indicate inefficiency and higher emissions, contributing to air pollution. In gasoline engines, black smoke may also indicate an overly rich fuel-air mixture.