How to Determine if Engine Combustion is Complete?

[DiGia]

Whether the gasoline has achieved optimal atomization and if the gasoline molecules are sufficiently fine. The quality of the air-fuel mixture; if the air is polluted, there may not be enough oxygen required for combustion. Whether the ignition efficiency is reduced; during driving, especially at low speeds, the ignition energy may decrease due to the numerous electrical devices in use. Whether the exhaust emits a strong and pungent odor, as if the gasoline is unburned, or if black smoke comes out of the exhaust pipe. This indicates insufficient air intake.