Losing Oil... don't know how

Schwamm

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2003 Mazdaspeed Protege, 2008 Mazda 3 Hatchback, 1984 RX7 GSL-SE
I just drove 800+ miles yesterday and this morning my oil pressure light came on. Looks like I am down at least a quart of oil, maybe 2. I have had problems losing oil for nearly two years, but I just did a bunch of maintenance that I thought would fix the problem. I was losing oil in this same way before this stuff, so I doubt the leak was caused by it.
Here's what I did before taking this drive:

Replaced valve stem seals - I had blue smoke on start-up before, and now I don't
Replace cam seals, crank seal, and valve cover gasket
Replaced timing belt, water pump, and radiator
Oil change

I do not see any oil visibly leaking under the car. I also do not seem to loose oil unless the car is running. It lost next to no oil over the previous two weeks, when I wasn't driving much.

So... where else could I be loosing oil? What else can I check? I am traveling currently and only have a few tools, so I might have to wait till I am home to do a lot of diagnostics. The car runs fine too, it just loses oil.
 
Yeah that did occur to me... is there any way to check for that, or is it more by process of elimination?
 
Actually I had a compression test done very recently. All cylinders were between 187 and 195 psi if I remember correctly. So good compression. I guess my piston rings are OK then.

I did check the intercooler pipes for oil residue a while ago but I can check again. Is any oil residue in the pipes at all indicative of a bad turbo? I remember seeing just a little residue but no drops or puddles of oil anywhere.

How can I check the PCV system?

Edit: no oil residue whatsoever in the intercooler pipes. Guess that means the turbo isn't spitting out oil?
 
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There is actually a lot of gunk near the where the engine and transmission meet. I'm wondering if it could be a bad rear main seal. Is that a common problem on these cars?

I'm going to clean it really well and see if the oil comes back.
 
Rear main is no more common than any other seal to leak. Turbo will spit oil into the intercooler pipes if the seals have failed, it could be from a stuck PCV valve. Shake it to see if it rattles, it is only a few dollars for a new one and you can get the Millenia S style that apparently handles boost better.
 
Could be slowly burning it up in the rings

I personally performed the compression test on this car about two months ago and it had awesome numbers for the mileage.

Austin, I'll text you later, but I'd go with the PCV valve first as well as modification of the PCV chamber in the valve cover. There is a write-up by 'The Man' for it.
 
How can I check the PCV system?

Here's what your PCV valve (a $6 part) looks like:
PCVcomparison3.jpg


...And here's where it's located (ignore all the ugly yellow crap from the pic I found of someone else's car..its the elbow shaped plastic thing coming out of the valve cover)
PCV_Catch1.JPG


You can probably even get to it with the plastic engine cover in place. Look right behind it, near the firewall.
 
I know what the PCV valve is, just wasn't sure if there was more to the "system" that I needed to check. I'll pick up a new OEM part and see what happens. Thanks for help

By the way, I remember the oil loss starting pretty suddenly about 2 years ago. I went to change the oil and found I was over a quart low, which had never happened before. It wasn't a gradual thing.
 
Finally got the new PCV valve installed. I thought my old one was OK because I can hear it clanking, but the new one moves much more freely and sounds different. I'll drive it another 1000 miles and see what happens.

Also, I noticed some of my vacuum lines have collapsed but I am not sure what they control. They run between the intake manifold and some parts that hook in to the wiring harness. What are these, and is this a problem?
7K5jFTj.jpg
 
They control the solenoids for the VTCS and VICS flaps, if they still function I don't think it matters much but I would replace them just to do it if it were my car.
 
So, it's been a few months and at least 500 miles and I have not lost any oil. 2 years of mysterious oil loss and all it was was a $20 part from Mazda. I feel dumb.

By the way, my old PCV valve moved and seemed OK, but compared to the new one it was very sluggish. If you're in doubt about yours, just replace it.
 
Lovely article here !
I have been having the exact same problem, I will change the PVC Valve tomorrow, and the valve cover gasket again with the proper torque and do a compression test a well in the coming weeks ! I always need to add 1 QT oil every 4-7 days
 
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