Question 492Motor Plants - Assistant Engineer

The correct answer is B) worn valve guides. Worn valve guides can allow engine oil to leak past the valve stems and accumulate in the exhaust piping or manifold. As the valve guides wear, they allow increased clearance between the valve stems and the guides, which permits oil to seep down into the exhaust system. The other answer choices are incorrect because: A) Collapsed hydraulic valve lifters would not cause oil accumulation in the exhaust. C) Excessive crankcase vacuum could potentially draw oil into the intake, but not specifically the exhaust. D) Excessive lube oil pressure would not directly lead to oil in the exhaust.