Review on Fel Pro 72401 O Ring by Eddie Man

Using this on a GM 5.3. If you notice low oil pressure on a COLD START, but the pressure builds as the engine warms up, then the o-ring on the intake manifold is probably worn and hardened, allowing oil to flow past it until it warms up and expands. , Your engine is low on oil, you may have jack noise caused by this problem and the top end also suffers from low oil. This o-ring replacement is just what you need. It's tricky to get to, you'll have to remove the front differential (if you have 4WD) and unscrew the steering rack bolts to get the oil pan off, but it's worth it. My oil pressure jumped from 20 psi cold start to 60 psi cold start and no more siphoning. I recommend using an o-ring lubricant (e.g. Super Lube, PTFE, etc.) on this o-ring prior to installation.