Here's why:
* White Smoke: White smoke usually indicates that coolant is getting into the combustion chamber (creating a milky substance in the oil) or, less commonly, that oil is burning. In your case, since oil is visibly leaking, burning oil is the more likely culprit.
* Oil Leaking at Exhaust Manifold: This points to the oil finding its way into the combustion chamber and then being expelled out the exhaust. The location indicates it's not a simple external oil leak; the oil is being forced out under pressure from the cylinders.
* Valve Stem Seals: These seals prevent oil from seeping past the valve stems into the combustion chamber. If they are worn or damaged, oil can leak into the cylinders, burn, and produce white smoke.
* Worn Piston Rings: Piston rings create a seal between the pistons and cylinder walls. If they are worn, oil can get past them into the combustion chamber. This is a more serious issue than failing valve stem seals.
Other less likely possibilities (but still worth considering):
* Cracked Head Gasket: While less likely given the location of the oil leak, a severely damaged head gasket could allow oil to leak into the exhaust system. However, you'd probably see other symptoms like coolant leaks, overheating, or low compression.
* PCV Valve Issues: A faulty Positive Crankcase Ventilation (PCV) valve can cause excessive crankcase pressure, forcing oil out. This is less likely to produce the volume of oil and smoke you're describing, but could contribute.
What to do:
This is a serious problem that needs professional attention. Driving the car in this condition will likely cause further damage and could lead to a catastrophic engine failure. Take it to a qualified mechanic for a proper diagnosis and repair. They will likely perform a compression test to assess the condition of the piston rings and valves.
Ignoring the problem will likely result in significant engine damage, possibly requiring an engine rebuild or replacement.
