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I've always found this to be the most annoying ongoing issue. For years my 1.8 swap used no oil, then all of a sudden it began to use oil and now my rear bumper displays the evidence. I resist using synthetic because it exasperates the issue. I tend to have short oil change intervals and I tend to add a quart every 1000 miles as of this post.
I'd like to begin a discussion on what your experience has been as to the main cause (for example, blow by that is getting sucked through the PCV system. Short term fix: oil catch can and long term fix: rebuild) This is what I presume to be the problem. My car has seen extensive daily driving and the 2-4 annual trips to the Appalachian mountains (TOTD, HWY 28 etc.) where it gets thoroughly worked by high rpm and high g-forces.
I've always found this to be the most annoying ongoing issue. For years my 1.8 swap used no oil, then all of a sudden it began to use oil and now my rear bumper displays the evidence. I resist using synthetic because it exasperates the issue. I tend to have short oil change intervals and I tend to add a quart every 1000 miles as of this post.
I'd like to begin a discussion on what your experience has been as to the main cause (for example, blow by that is getting sucked through the PCV system. Short term fix: oil catch can and long term fix: rebuild) This is what I presume to be the problem. My car has seen extensive daily driving and the 2-4 annual trips to the Appalachian mountains (TOTD, HWY 28 etc.) where it gets thoroughly worked by high rpm and high g-forces.
Thanks everyone!
Could be valve stem seals, could be rings. Do a compression test and leakdown to determine if it's either, and then use your judgement to determine if it's worth fixing.
You are asking the wrong question. Who cares why someone else engine burns oil. Lets find out why yours does.
A bit more detail would help:
compression ratio
piston brand
ring brand
valve seal brand
mileage since last head rebuild
mileage since last bottom end rebuild
boosted, what type
redline
track or street use
leakdown numbers
compression test numbers
Sorry to hijack your thread: Question to the pros: If you have oil consumption clearly going to the exhaust, is that only from ring blow by and valve leaks (seals or seats) going through the PCV and back into the intake? Or is it possible that the oil can go the other way and sneak UP past the rings and get consumed/burned in the chamber?
I was getting plenty of blowby and using about a quart a thousand. Comp test was good so bought a leakdown tester and had about 50% on #3. Turns out I am missing some ringlands, no big deal. If your leakdown looks iffy, stick a bore scope in there and see what shows up, or in my case is not showing up
New engine on a stand, waiting for the snow to melt first.
The bore scope I used was 1080 resolution or greater. Turns out it is a piece of ****. Took me about 15 mins to get something even vaguely in focus. I didn't take the pics for the Wikipedia entry on broken ringlands, I kept them for a record for myself. Sorry they don't meet your exacting standards but I'm also not trying to sell a product with these photos.
You are asking the wrong question. Who cares why someone else engine burns oil. Lets find out why yours does.
A bit more detail would help:
compression ratio
piston brand
ring brand
valve seal brand
mileage since last head rebuild
mileage since last bottom end rebuild
boosted, what type
redline
track or street use
leakdown numbers
compression test numbers
well....I care! This thread isn’t all about me!
-OEM 04 engine with 99 head. I assume that the C/R remains 10:1 unless there is difference between on combustion side of the vvt head and the 4W.
-Mazda
-not sure about valve seals but head was rebuilt about 70k ago.
-bottom end is still OEM 170k
-NA
-7,000
-street use, occasional track days
-don’t have leak down or compression numbers. Yet.
The bore scope I used was 1080 resolution or greater. Turns out it is a piece of ****. Took me about 15 mins to get something even vaguely in focus. I didn't take the pics for the Wikipedia entry on broken ringlands, I kept them for a record for myself. Sorry they don't meet your exacting standards but I'm also not trying to sell a product with these photos.
Ah, borescope, not potatocam. We bought a Snap-On borescope about 5 year ago. Cost about one million dollars. Image quality was ****. Next year we bought a Harbor Freight borescope with several additional features, for like $120. Image quality is great. Last year I bought a borescope attachment for my phone for like $40 off Amazon that takes even better pictures
Not sure what the lesson there is other than some supposed high quality imaging devices aren't and the phone in your pocket is probably the best camera you have.
-OEM 04 engine with 99 head. I assume that the C/R remains 10:1 unless there is difference between on combustion side of the vvt head and the 4W.
-Mazda
-not sure about valve seals but head was rebuilt about 70k ago.
-bottom end is still OEM 170k
-NA
-7,000
-street use, occasional track days
-don’t have leak down or compression numbers. Yet.
Two subjects covered in this thread. Diagnosing your car and the wider question of oil consumption in BP's. It's a good question, thus the request for a thread and data points.
In your case, I'm guessing it's simply time for rings. Without a reroute, #4 is usually toast by 170k. BP sump should fluctuate between atmo and very slight positive pressure. If a ring(s) leak compression, the crank case is rarely at atmo and positive peaks are higher. This pressurizes the cam box via the drainback holes, which in turn forces oil vapor out via the path of least resistance. That could be valve guides, valve seals, PCV. Leakdown will answer your question. Take your time doing it. Depending on cam position during test, you may hear air in other cylinders, intake or exhaust. Those are valuable clues.
Sorry to hijack your thread: Question to the pros: If you have oil consumption clearly going to the exhaust, is that only from ring blow by and valve leaks (seals or seats) going through the PCV and back into the intake? Or is it possible that the oil can go the other way and sneak UP past the rings and get consumed/burned in the chamber?
Don't know for certain, but I would guess that crankcase gases (and suspended oil) that are under more pressure from normal (owing to subpar ring seal) have no problem finding their way past those aforementioned subpar rings under decel and cruise conditions. IOW, plugging the PCV is not going to stop oil consumption in a motor with a worn-out bottom end.
In your case, I'm guessing it's simply time for rings. Without a reroute, #4 is usually toast by 170k.
reroute installed with rebuilt head. I recently replaced the timing belt, water pump seals etc. going back together I noticed that the PCV hose where it goes over the PCV was loose-ish, I used a hose clamp to tighten it down and increase the seal to the PCV valve (recently replaced).
is a PCV breather (in leu of the piping to intake) be ok? I’ve never done it before l, but I wonder if it would stop the suction effect of oil vapors into the intake. I understand that the PCV only really opens with you have some vacuum and closes under wot, but the other end is always open to the intake. Correct me if I’m wrong but I could see plenty of nasty oil vapors being sucked into the intake through this tube.
reroute installed with rebuilt head. I recently replaced the timing belt, water pump seals etc. going back together I noticed that the PCV hose where it goes over the PCV was loose-ish, I used a hose clamp to tighten it down and increase the seal to the PCV valve (recently replaced).
is a PCV breather (in leu of the piping to intake) be ok? I’ve never done it before l, but I wonder if it would stop the suction effect of oil vapors into the intake. I understand that the PCV only really opens with you have some vacuum and closes under wot, but the other end is always open to the intake. Correct me if I’m wrong but I could see plenty of nasty oil vapors being sucked into the intake through this tube.
Speculate endlessly: Maybe guess right. Maybe not. Definitely spend more time and money than needed to correct the issue.
Do leak down test: Know the truth instantly. Act accordingly
NB1 OEM PCV system works pretty well on a healthy engine. Fancy breathers, separators, return lines, valves, unicorns don't have any effect on oil control with a sick engine.
01-02-2019, 06:47 AM
Oil Burn
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