Excessive oil consumption - part 2

I had a post going in this forum asking questions about the excessive oil consumption I've been having for the last 20000 miles. I don't know how it got removed from the server, but here's the summary.

I had mentioned that I had very good compression test results (all cylinders greater than 190 psig, all even), and that a leakdown test noted that while the compressed air in the cylinders leaked past the rings to the crankcase (and out the dipstick), that the leakage was within the "green" range on the gauge, and all 4 cylinders measured similarly.

I have a catch can installed between the PCV valve and the intake manifold. It is pretty small (Kobalt $10 model from Lowe's), and fills up near the bottom of the copper filter after driving through a full tank of gas. I dump that back into the filler on the valve cover every time I get gas.

The air hose from the valve cove to the intake doesn't seem to have any oil in it, probably because the flow is from the intake to the valve cover.

The following pictures (shutterfly link below) were taken of the exhaust, intake, throttle body and EGR last weekend. The exhaust soot seems just a bit more than I expected. You can see some dislocations in the surface, where it probably has 2 layers. The intake was pretty much filled with soot, from the EGR system, but had some wet parts from the oil. That was noticed about 2-3 inches from the intake manifold outlet, through some of the intake port on the head. The valves were clean. You can see that the fuel injectors kept the upper portion of the intake ports clean.

None of the valves were wet after feeling each one. I assumed that if the valve seals were in need of replacement, some oil would be evident on the tops of the valves.

Again I'm not sure where I should look. I didn't find oil in the valves, but I did find it on the gasket between the intake manifold and the VTCS runners on the IM. There was oil where the PCV tubes connect to the intake manifold. Then, the intake manifold outlet runners were a bit moist with oil 2-3 inches UPSTREAM of the head.

I know that the soot and oil are normal for modern engines with PCV and EGR systems. I understand the value of these systems, so I'm not planning on removing them. However for diagnostic purposes, I would consider disabling them (in a manner that wouldn't trip the check engine light) temporarily to help diagnose the problem.

I also have a picture to show that there isn't any oil dripping from the oil filter. There haven't been any signs of oil leakage onto the exhaust or the floor of my garage.

Any ideas or suggestions would be greatly appreciated.

Thanks!

http://share.shutterfly.com/action/welcome?sid=8AZuGjdizcNWX4

get the millenia pcv valve that were using on our turbod cars

I read up on that. I figured that the catch can would take care of the problem. What was the major difference? I'll put it on my list of things to try.

Thanks

I forgot to mention (from the lost post) that I'm adding .5-1 quart of oil every 400 miles.

I added the millenia valve and saw no difference in oil consumption...still using a quart or so every 1000.

I think what I need to do is disable the PCV system temporarily, and see what changes with the oil.

I understand that PCV vents combustible gases in the crankcase, and relieves pressure. Older cars didn't have them, so am I risking damage by blocking the PCV?

How do your spark plugs look? The fact you have good compression doesn't necessarily mean the rings and cylinder walls are good. In a compression test you are using the cylinder to pump a small amount of air into a gauge, the gauge traps the air to give you a reading. The combustion process has a much greater pressure and it happens at a much faster engine speed than a simple compression test.

You said the leak-down test showed within the green limits but air was blowing out the dipstick hole. I have one of those gauges with a green zone at anything above 40%. That means you could have 40% percent of the air blowing by out the valves or around the rings and be considered OK. A good healthy engine should not exceed 10%. Anything greater should be suspect. Any good engine build shop would be looking for less than 10% leak-dowm

What I see in your photos looks like some pre-emission engines I have torn down. I don't consider it clean for a modern engine.

I don't think you are going to solve the problem by removing the EGR or blocking the PCV. I believe your engine needs a rebuild. Sorry.

Clifton

^^unfortunately I am beginning to think the same thing about my own car.
I am having the same problem, 1 qt every 1000 miles or so and it doesn't appear to be all that uncommon now that a lot of our cars are going +100k, like my own. I see more of these kind of posts every week.

BTW, iluvmacs...how long have you been outta Monroeville??

Anyway, I was gonna pull my plugs this weekend, they are due, anyway.

are you running synthetic or dino oil?

I've notice a fairly significant difference in the amount of oil I go through with synth, about 1 q every 2-3k miles versus dino, which is hardly any. Not sure why though I've heard that synth burns much easier then dino oil.

jlanger said:

are you running synthetic or dino oil?

I've notice a fairly significant difference in the amount of oil I go through with synth, about 1 q every 2-3k miles versus dino, which is hardly any. Not sure why though I've heard that synth burns much easier then dino oil.

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Why would this be? I have long wondered if the fact that i switched my car from dino to semi-synthetic around the time that I bought it (58k miles) made a difference (and caused my consumption). It would be nice if the solution was this simple. Part of me wants to go back to dino and experiment, but my car has 82k on the clock now, and I don't really think it's good to be switching back and forth like that. Thoughts?

shouldnt matter switching back and forth. just make sure you do ur oil changes when mazda says witch i think it is 3k miles. or every 6 months (not sure about 6 months.

I don't think change intervals have anything to do with it...the interval is more about how long it takes the oil to break down and stop properly lubricating than it is about any need the engine has for "fresh" oil.

EviLMaN said:

shouldnt matter switching back and forth. just make sure you do ur oil changes when mazda says witch i think it is 3k miles. or every 6 months (not sure about 6 months.

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Every 5,000 miles is the recommended interval, or every 6 months.

slavrenz said:

Every 5,000 miles is the recommended interval, or every 6 months.

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Running synthetic you're supposed to be able to double that, however I've seen that running synthetic "seems" to burn off more oil, the question is since I'm now changing my oil every 3-5k versus 10-12k, there probably is going to be a difference. From what I can find out about it online, it's not proven yet but many people suspect that since synthetic is so much better at getting into small spaces to lubricate parts, it tends to leak out of older gaskets and such. However I can't find any "proof" of this.

Interesting thought though, I just replaced my EGR valve and was going to set up a poll about synthetic vs dino oil and replacing that valve.

my oil consumption is gettin worse. im now going thru 1quart/200km.
used to last me 500km before.

i too have tried the alternative pcv without success.

I was going through a bit of oil between oil changes... Turned out to be the rear main seal. And no, it wasn't visibly leaking at the trans case/rear of the motor. However, the inside of the bellhousing was caked with 1/4" of clutch dust/oil mix.

The reason synthetic burns more is because the molecules are smaller and more consistant in size, therefore they leak out more easily.

Mike R said:

I was going through a bit of oil between oil changes... Turned out to be the rear main seal. And no, it wasn't visibly leaking at the trans case/rear of the motor. However, the inside of the bellhousing was caked with 1/4" of clutch dust/oil mix.

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I am really curious how you figured this out. My car seems to run just fine
other than the missing oil and there's no leak and no excessive smoke. I just swapped out my plugs this past weekend and the tips were clean and only
small amount of carbon buildup around the bottom of the plug after about 25k miles.

I found it when I totalled the car by hitting a large metal bar on the highway. That punched a hole in the trans case and ripped a 14" gash in the floorpan. I found the leak when I pulled the trans to repair it. I was quite surprised how much oil was inside the bellhousing.

Oli consumption goes up as the engine wears. It is 'blow-by gasses' pushing oil out of the PCV.

Not a problem (worth a rebuild) until it gets a lot worse...

P-Funk! said:

Oli consumption goes up as the engine wears. It is 'blow-by gasses' pushing oil out of the PCV.

Not a problem (worth a rebuild) until it gets a lot worse...

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My car barely uses a half a qt between 7-10K synthetic oil changes since the rear main was replaced, used a more than a qt prior. The car has 202,000 miles on it.

^Oh, i agree. Mine consumes very little at 180K miles...