Which component would NOT lead to an engine oil leak?

The option indicating a stuck open PCV valve would not lead to an engine oil leak because its primary function is to control the flow of gases in the crankcase and maintain proper pressure. When a PCV valve is stuck open, it allows excessive crankcase vapors to be drawn into the intake manifold, which can lead to increased vapor loss and potentially contribute to an oil consumption issue. However, this condition does not create a path for engine oil to escape the engine, hence it does not result in an oil leak.

In contrast, the other choices involve components that directly contain or manage oil within the engine. A cracked valve cover gasket allows oil to seep out at the top of the engine, while a worn rear main seal can lead to significant oil leaking at the rear of the engine where it connects to the transmission. Worn piston rings can cause oil to enter the combustion chamber, leading to oil consumption and exhaust smoke, but they also do not create a direct pathway for oil to leak externally. Understanding these differences is essential for diagnosing oil leak sources in an engine.