I share this opinion.

I replace the CCV and all hoses and clean out the air distribution manifold about every 60k miles. Use the cold weather version of the CCV, the insulated hoses and if you live in a really cold area - retrofit the cold weather dipstick - it eliminates the baffle that gets clogged. At the same interval, I use a can of BG Products "EPR" (aka BG109) to keep the rings unstuck. I have 148k miles on my 3.0i/M54, bought it new, and it uses virtually no oil.

I have 1 car on each system, but I do have a pressure relief built into my PCV conversion for instances where the crankcase might become pressurized. The PCV valve is designed to work on an "open" crankcase. The conversion kinda works but does rely on a little bit of luck and some air getting into the crankcase.

For those with the original CCCV you can get rid of the moisture build up (and freezing) by letting a little fresh air into the system. letting the engine idle for even 1/2 a minute with the oil cap off, just before you shut it off, once in a while makes a big difference, but yes, a PITA but a good test . The better answer would be to drill and tap a small hole at the back of the valve cover and install a small orifice and filter to let a little air in.

I am trying to figure why this mod (more vacuum in crankcase) reduces oil consumption, and I think I have the answer (any engineers in forum?).

Quick review on 4-cycle engine: Intake, Compression, Power (Explosion), Exhaust.

- Compression, Power strokes have positive pressure inside the chamber (thousands of psi), creating blow-by.
- Exhaust is kind of neutral, maybe hundreds of psi or close to 0.
- It is the Intake phase that creates suction in the combustion chamber (thus the vacuum in the Intake Manifold).

My 1998 528i M52 has no oil consumption, even at 165K miles.
My 2006 X5 M54 has brand-new CCV and drinks about 1qt/500 miles. From reading mlody post and blog (aka ElbowGrease on youtube channel), the oil ring (the bottom ring) is low-tension and has a gap of 2.5mm after some 120K miles. This gap allows oil to sneak up and sucked into the chamber during intake stroke.

- My X5 Stock brand-new CCV: when removing oil cap, there is a slight hiss but no big deal, so the vacuum is not much.
- My X5 AFTER CCV Mod: when removing oil cap, there is a moderate hiss, so the vacuum is more than stock.


When the M54 is new, the gap is small (? 0.4mm), so virtually no oil sucked into chamber.
As mileage adds up, this low-tension ring wears out, creating the gap of 2.5 mm.

Anyway, the work around CCV mod that increases crankcase vacuum reduces oil consumption.

So, this is my theory, feel free to correct me. Numbers are arbitrary strictly for discussion...

1- Stock CCV: there is not enough vacuum in crankcase (neg 16 in Hg and neg 4 in Hg = difference of 12 in Hg), during Intake stroke, the differential in vacuum allows oil to be sucked into the combustion chamber ---> oil burned.

2. CCV Mod: now there is more vacuum in crankcase, close to I.M. vacuum (neg 16 in Hg and neg 12 in Hg = difference of 4 in Hg), during Intake stroke, the differential in vacuum is not enough to drive oil into the combustion chamber ---> very little or no oil burned.

Anyway, just a theory and would love to hear from some engineer gurus out there.

- First photo is the principle of 4-cycle engine.
- Second photo is Stock vs CCV Mod.



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Very good theory! That does make some sense. :) I think also though there is another factor involved that has been addressed by some of the guys doing the mod. I think the BMW engineers got a little bit sloppy on the design of the valve cover baffle and in the way the vent tube comes off the valve cover thinking that the oil seperator would take care of any oil that got sucked in to the CCVC. By doing the mod (depending on how you go about it) there is less chance of the little bit of oil that collects on the bottom of the valve cover tube to getting sucked out.

As far as the freezing/moisture problem I think of it this way, The crankcase is closed so it is filled with moisture saturated combustion gases. The moisture ends up forming dropplets, which get seperated in the cyclone oil seperator, which ironically works much better seperating heavey moisture droplets than it does oil, and returned to the crankcase. The CCCV can only get rid of moisture vapour not droplets, so the only way to reduce the moisture is to let in a little unsaturated atmosphere to absorb it and let it get sucked through the seperater and into the intake as vapour.

I think you are on the right track. I'd offer that the lower oil control ring gets sludged up and sticks to the ring land. In order to be effective, the ring needs to spin. Some of the piston pics on E46Fanatics are disturbing.

My 2006 X5 M54 engine used to drink 1qt/400-500 miles.

Did the LOWER engine treatment (don't have time to do UPPER treatment with AC Delco thingy). This is what I did:
- 3/4 qt ATF in engine oil for 200-300 miles.
- At oil change, used Lubro Moly Engine Flush, ran engine for 10 min, then replaced oil + oil filter.
- Oil consumption is still the same, i.e., 1qt/400-500 miles

Then I did the poolman, Bavarian CCV mod, 500 miles later zero oil consumption!!!


I am very convinced that my theory above (more crank case vacuum ---> much less oil gets sucked into combustion chamber) is correct.

The key thing is the PCV Valve reducing the flow to appropriate level (3/4-inch ---> 3/8-inch). Some people on youtube didn't use the PCV Valve but they used plumbing adapter to bring it down to 3/8" or so. I still recommend the PCV Valve. Just replace/clean it every 10K-15K or whatever interval you are comfortable with.


This is my setup, thank you all for contributing.



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UPDATE: Zero oil consumption after 500 miles with CCV Mod.

2006 X5 3.0i M54 engine 6sp MT with 122K miles.

1. Did the LOWER end treatment:
- 3/4 qt ATF for 200 miles.
- Ten (10) minutes before oil change, one bottle of Lubro Moly (500 mL) into engine oil. Ran engine at idle for 10 minutes.
- Changed engine oil and oil filter.

---> No change in oil consumption: still 1qt/400-500 miles!


2. Did the CCV Mod (Duralast 1124 Valve as in the photos).
- After 500 miles, zero oil consumption, unbelievable.
So this CCV Mod rocks!!!

Thank you all for saving my motor!!!

I think there is pilot modification only hose from vent in ccv to the back of the manifold and you got same effect of vacum
I think it's done by 50s kid on e46 on YouTube

IMO there is no connection to eliminating the oil consumption and that it is good, or bad, for the engine. Would anyone do this on a new car?