What causes exhaust engine smoke and gas smell in exhaust?

Exhaust engine smoke and gas smells can be caused by several factors, including incomplete combustion of fuel, oil leaks, or a malfunctioning engine component. Blue smoke typically indicates burning oil, while black smoke suggests excess fuel is being burned. Additionally, a rich fuel mixture or a failing catalytic converter can contribute to strong gas odors in the exhaust. Regular maintenance and timely repairs are essential to mitigate these issues.