Air jetting from the oil filler cap tells you nothing, I'm afraid. Even a
brand-new engine, freshly broken in and at max oil life will exhibit
/considerable/ jetting from the oil filler cap. From oil filler neck
emissions alone, it's hard to tell the difference between the blowby of a
worn engine and a new one.
You need to have a garage perform wet and dry compression tests. Keep in
mind even these are only analogs for oil ring condition. It is possible to
have good oil rings and poor compression rings, and vice versa.
That's a quart every 1,200 miles. Not good at all for less than 200K
The idea that a plugged PCV valve by itself will increase oil
consumption is common but erroneous.
A good sign.
I suppose it's possible. The oxygen sensor would detect the excess
hydrocarbons from the oil and compensate by reducing injector pulse
Modern motor oil is a readily and cleanly combustible hydrocarbon mix.
Can you supply a clear photo of the plugs?
Smoke on overrun indicates worn rings, not valve guide oil seals.
I think you need to have a compression test done. If the readings go up
for the wet test, the rings are very worn.
They won't necessarily fail all at once, but it only takes one cylinder
to fail for smoke to show out the tailpipe. Two things you can have in
that case: A slightly lumpy idle, and an odd-man-out compression test
reading on one cylinder.
I have a feeling you'll find that one cylinder has much lower
compression than the others.
If one cylinder is much lower than the others, there's a tiny
possibility that the rings are simply carboned up and not sealing as
they should. In that case, long-term use of Mobil 1 and some occasional
spirited driving may free it up.
By the way, when was the last time you checked the valve clearances?
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.