Bad PCV causing motor to burn a little oil?

[JustinH]

My girlfriends 2000 plymouth neon...

The car has about 85k miles on it, runs great.

I keep up on the maintenance on it.

I've been going with supertech filters and supertech dino oil for the past 30k miles or so, at 4k intervals. 5w30 was the weight.

All of a sudden the car started using about a quart of oil in a 4k mile duration.

I switched to a 10w30 supertech HM oil, and its still using a quart or so, maybe a little more.

The car doesn't smoke or anything, isn't leaking a drop.

I changed out the factory PCV valve the other day.

Would that help the consumption issue?

Does the PCV have anything to do with fuel economy?

Even though this car runs great, it doesn't do so hot in the fuel economy department (low to mid 20's).

Thanks,
Justin

 

[va3ux]

Oil consumption can be via :

PCV
Rings
Valve Stem seals
Leaks (seals, gaskets, etc)

My 2.7 uses a reasonable amount of oil but does not smoke at all. In my case I'm willing to bet that 50% (maybe more) is via the PCV. The interior of the Intake plenum is always coated with fresh oil. Quite common with the 2.7, and is due to the poor design of the PCV system. Can't say if the PCV system is a typical source of oil consumption on the Neon or not but it is not out of the question. A gummed-up PCV valve that stays open all the time certainly *could* increase oil consumption, depending how the rest of the sytem is designed.

PCV is an emissions control device. It scavenges blow-by gases from the crankcase and returns them to the intake system where they can be re-burned. It really doesn't have anything to do with fuel economy.

 

[Donald]

You say you changed the factory PVC valve, so I assume you mean original? If so it needed to be changed anyway. But how did the old one look? Its a one way valve and you can test it with a little thought.

 

[JustinH]

Yes it was the OEM mopar PCV valve. I just tossed it, didn't look too hard at it.

 

[Donald]

I would be interesting for you to see if the oil loss is linear over the OCI, or is it worse as the oil is in a more used condition.

A compression check would tell about the rings.

A cleaning/rinse with Auto-Rx may help if there is crud in the ring pack causing less than perfect sealing. It may also improve mileage and would be worth the $20 to me to try it.

 

[kargo27]

I was talking to a lady the other day at an oil change place and she said that she traded in her Neon with 150k miles on it and get this...had only spent about $500 in repairs over the life of the car. And that repair was on the A/C.

I told her that she should have contacted Chrysler about that stellar performance. That rivals Toyota.

 

[JustinH]

Yep this one runs like a top.

So far I've changed fluids in it, and other than wear items, the only part that needed to be replaced was a radiator, when i took a rock in the plastic end tank, it was a goner.

 

[va3ux]

I don't think I've spent $1000 on repairs on my Intrepid, it now has 202K on it and it's in it's 8th year. No complaints here.

 

[wiswind]

It is possible for a PCV valve to cause excessive oil consumption.
It is a 1 way valve, with a spring that decreases the opening slightly as the vaccum increases.
At Idle, the vaccum is at maximum, and the PCV valve opening will be at its minimum.
However, the actual flow rate would be the same.....smaller opening with more vaccum.

If the valve sticks, it could result in too much flow....which would increase the possiblity of pulling oil droplets from the engine.

There have been posts about some aftermarket PCV valves not being as accurate in metering the flow as the OEM.

You don't want to pull too much...and increase oil consumption.
However, you don't want to pull too little, as it is important to remove harmful vapors from the crankcase to prevent oil break down and / or sludging.

Don't get me wrong, the flow rate through the PCV valve is not as critical in specification as fuel metering by a fuel injector, etc.....however, it is important to be within a certain tolerance.

 

[mechtech2]

A qt or more in 4,000 miles is a lot by today's standards - esp for a small engine.
Is the exhaust pipe oily inside?
Because I'm not buying no leaking or burning.
How about a getting the compression checked?

 

[Towel_Rail]

Check the owner's manual -- I would bet that 1 quart per 4000 miles is within the acceptible range. Even if it's more than you'd prefer for an 85,000 mile car.

With a new OEM PCV valve, I think we can rule that part out.

Try a round of Auto-Rx perhaps?

- Scott

 

[Lazy JW]

I doubt you would get ANY manufacturer to say that one quart of oil consumption in 4k miles is excessive.