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Guest Message by DevFuse

* * * * * 1 votes

Mysterious Oil Consumption? Change your PCV Valve!

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33 replies to this topic

#26 Juan


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Posted 24 March 2014 - 10:02 AM

Job location changed and I ran two quarts low all of a sudden *(over six months) when I began driving 30 minutes round-trip per day at speeds of 65-75 mph at 3k+rpm. I NEVER had a problem with oil consumption over same milage/time interval traveling surface streets to work -the Subie shop would have mentioned it, right?


I'm back to surface streets, new job location, same milage/time interval and have added 1/2 quart over past six months to keep it topped up.


Sure, NOW I check my oil at each fill up.

Sure, NOW I'm going to replace the PVC valve.

Sure, NOW I'm going to ask the Subie dealer, 30+ oil changes and 100,000 miles since new, why they have never mentioned PVC valve.


I have never believed in 3,000 mile oil changes. I peg it at 5,000.


When is the best time to check oil level? Stone cold? Fire hot? Luke warm?  I get different readings between the notches/holes at different temps.

#27 Fairtax4me


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Posted 24 March 2014 - 01:12 PM

I always check first thing in the morning before the car is started for the day.
This allows the oil to settle into the pan overnight, and ensures the oil level will be accurate. After the engine has been running a lot of oil is still in the heads and dripping down from the block.
If you check the oil level immediately after turning the engine off, then check again an hour later you will get different readings as the oil settles out of the crank-case back down into the pan.

#28 Cougar


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Posted 25 March 2014 - 09:54 PM

I helped a friend out some time ago with his Loyale that was blowing so much smoke out the tail pipe is was like going through a smoke screen. Fortunately he had a new spare PCV valve in the garage. We changed it out to see if that worked and then there was no more smoke. Easy fix.

#29 lmdew



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Posted 26 March 2014 - 05:05 AM

2003 2.5 Impreza SOHC had been using approx. a 1qt every 200 miles.  


- New Subaru PCV help some but did not cure the usage

- All Hoses hooked up correctly

- Only 3% leak down

- No External leaks

- Seafoam no change

- MMO no change


- Last attempt ran the Gunk Engine cleaner at idle for about 30 minutes (way longer the specified on the instructions) as it worked I could hear the engine change.  So far so good, 200 miles and no oil usage, no smoke.  Only 154K on the motor with new HG due to the bent valves of the timing going for the PO.  I usually would not use the Internal "Cleaners" but I was down to pulling the engine apart so nothing to loose.

Edited by lmdew, 26 March 2014 - 05:05 AM.

#30 MilesFox


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Posted 26 March 2014 - 08:51 AM

My 98 forester with frankenmotor and new seals was using 1 qt a week. i was able to reduce consumtion to 1 qt every 2 weeks by replacing the PCV valve, until the ring land broke. i'm sure the oil was being used past the rings as well, but the PCV did help a lot in that regard.


I have had success rejuvinating old oem PCV vlves by sea foaming them.


I work at an oil change shop, and some later model cars come in with low oil at 3000 miles, and these are cars with moderate miles, and unserviceable PCV's. I noticed toyota uses the same type of pcv, but unfortunately, our shop doesn't stock this type of PCV valve.


And with failed pcv valve in mind, there are some late model engines coming in with 'rear main seal leaks', and i would bet suggesting a PCV valve would help that.

#31 subnz


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Posted 28 March 2014 - 02:36 AM

usally give mine (PCV valves) a good swim in petrol and that does the trick.

#32 forester2002s


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Posted 28 March 2014 - 03:14 PM

I spray WD-40 into the PCV valve periodically,  and then give it a good shake before reinstalling it.


After doing this for 10 years on my Forester, I felt guilty and bought a new PCV valve. But I've kept the old one as a spare, because it seems to be perfectly serviceable.

#33 efseiler


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Posted 31 March 2014 - 08:21 PM

For the lack of a $15 part, engines are lost.


That reminds of something I read in MAD magazine years ago...



Problem:  Screw broken.

Solution:  Replace entire engine.


a.k.a  How union labor stays in business.

#34 efseiler


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Posted 31 March 2014 - 08:32 PM

I've had problems with oil consumption like that....sometimes I drive 100 miles and it's down like almost an entire quart.


Other times I've gone almost 3000 miles and it's down only like a quarter quart.


It depends a lot on what you're driving through but weird stuff does happen...I got a bunch of stories about that.




I use Lucas additives in the pan and tank...it doesn't cost much and basically works.

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