The smoke emitted from petrol engines are catagerized into three types:
1) White ( Normal combustion, visible in cold weather from tail pipe. This is steam which condensed at exhaust tail pipe and forms into water droplets)
2) Black smoke - generally at acceleration pointing to a rich fuel mixture. Meaning less air and high petrol ratio. Fuel system and air intake problems.
3) Blue Grey Smoke - Engine oil entering into combustion chamber. Due to weak engine. Through piston oil rings or cylinder head valve seals.
