If you find oil in your intake manifold, it's not something that should be ignored, but what has caused it isn't always clear. Here the most likely culprits.

The PCV valve not only improves vehicle emissions, but also engine efficiency, reliability, and power. By redirecting the blow-by gasses back into the intake to be burned, the engine can receive ...

Separating the crankcase from the intake manifold, which is a source of varying air pressure, the PCV valve maintains the optimal level of vacuum in the crankcase to extract the products of blow ...

In this picture, you see Jason has upped the ante with a nice-looking billet PVC valve that's plumbed to a vacuum port in the intake manifold with a rubber hose. See All 20 Photos ...

So, the bottom line is that excessive oil vapor in the intake manifold is detrimental to your engine. The fix is to install an Elite Engineering PCV catch can, and here's how! See All 9 Photos ...

Besides a damaged PCV system, a few other issues can cause oil to get into your intake manifold. Another relatively common issue is worn piston rings or damaged cylinder walls.