Another Catch Can Question

So I dump my carch can every thousand miles or so. And check oil at the same time. Question is where does the oil in the catch can come from? Oil is always full on dipstick.

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Positive Crankcase Ventilation (PCV) system. It redirects blowby from the engine back to the intake.

The amount is small compared to the capacity of your oil system when up to the proper level. Remember, not all your oil drains back to the pan when the engine is shut off.

cubmedic said:

So I dump my carch can every thousand miles or so. And check oil at the same time. Question is where does the oil in the catch can come from? Oil is always full on dipstick.

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It's not totally oil. If you smell it it will have a gas odor to it. The pvc vents vapor, boil off and blow by, the catch can slows this vapor down and condenses it turning it back to liquid. So even though it looks like oil and may even have an oily feel its actually just garbage that's not being reintroduced bake int youre motor.

Ramnewbie said:

It's not totally oil. If you smell it it will have a gas odor to it. The pvc vents vapor, boil off and blow by, the catch can slows this vapor down and condenses it turning it back to liquid. So even though it looks like oil and may even have an oily feel its actually just garbage that's not being reintroduced bake int youre motor.

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That makes since. Thanks!

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Hey so to chime in on this ive recently noticed on my 2011 ram 1500 5.7L hemi i did a oil change and drove it now checking again i find my dipstick smells like raw gasoline any thoughts?

Kevdog, the first thing I would do is change your pcv valve.

kevdog999 said:

Hey so to chime in on this ive recently noticed on my 2011 ram 1500 5.7L hemi i did a oil change and drove it now checking again i find my dipstick smells like raw gasoline any thoughts?

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Its going to be blow-by.

If your PCV is not working, you will have a lot of blow by building up in your oil and IVIC will be telling you to change your oil early.

Do you have a catch can?

The Hemi's comparatively higher compression, and the reduced number of rings and shorter piston skirts on modern engines means more unburned crap gets into the crankcase.

If the PCV IS working and you do not have a catch can, all that funky milkshake goes back into your throttle body. Motor oil, even highly diluted motor oil, does not burn cleanly--it leaves varnish-like residuals and since the Hemi is not direct injected it leaves them on the intake valves and seats when it contacts hot metal on a warm engine. It also leaves oily build up on your intake and can foul your TB over time. Oil in your air-fuel mixture also can cause pre-detonation which forces the PCM to pull timing costing you power.

Good to know pcv will be changed thanks!