TOP SECRET Oil Catch Cans and Oil Caps

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The 370 (like all modern cars) has a PCV system, which you can basically think of as a one-way-valved tube from the crankcase back into the intake. It's using intake vacuum to scavenge vapor from the crankcase so that the crankcase's pressure is regulated (otherwise it would build up pressure and blow oil seals, etc).

The crankcase vapors are mostly oil vapor, so the PCV system basically puts a small amount of oil into your air intake at the intake manifold. The idea with the catch can is to put a baffled can in the path of the vapor flow so that most of the oil will condense out and collect in the can, rather than get fed to your engine to burn. Should result in a cleaner engine over the long haul, and slightly increase the effective octane rating of your A:F mix.

The tradeoff is now you have another maintenance item to take care of: emptying the catch can of condensed vapors every once in a while. On our cars, when not forced induction anyways, dumping a can every 2-3K miles seems prudent. If you allowed the can to fill up to the point where corner G's could push the oil back out into the PCV lines, it could be ugly I imagine (at the very least, the engine would stumble from having a sizable quantity of liquid oil sucked into the intake all at once...).

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