What is a consequence of excessive oil in the airbox?

Excessive oil in the airbox can lead to external leaks due to high crankcase pressure. When there is too much oil in the airbox, it can create an imbalance in the crankcase system. This imbalance results in increased pressure, which may cause oil to leak out of various seals and gaskets in the engine. High crankcase pressure can also disrupt normal engine operation and can lead to further mechanical issues if not addressed.

Understanding this effect is crucial for maintaining engine health. The other options do not accurately depict the consequences of excessive oil in the airbox, as they suggest improvements in performance or efficiency rather than the detrimental effects that high crankcase pressure can cause.