5.7 using oil, no smoke

[Wozny]

My 1992 5.7L uses a quart every 60 miles and doesn’t leak or smoke. I do see a little smoke when I take the oil filler cap off but it’s not much, and there’s no smoke out the tailpipe. I don’t think it’s leaking only on the road, because I’ve tried stopping along the road and checking for drops, but there’s none. The compression is around 120-125, pretty low, but if it was burning a quart every sixty miles by the rings or valve guides, wouldn’t it be smoking like a chimney? Well thanks, any and all suggestions would be greatly appreciated because I’m at my wits end

 

[Wozny]

Forgot to say, it’s got 140,000 on it, I just got it and don’t know how well it was maintained but the oil was black as coal when I changed it

 

[RawbDidIt]

Mine burning oil, but nearly at the rate yours is, but pretty bad. About a quarter every 1500 miles. No visible smoke from exhaust, but a lot of carbon on the fender above the tailpipe. A quart every 60 miles is a lot. Regardless of whether it's smoking or not, it needs a rebuild

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[thinger2]

Thats an engine thats never had an oil change.
I suspect you have multiple issues to go through that much oil.
Part of it is going past crispy fried valve stem seals and getting burnt.
Some of it is going through the pcv and back into the throttle body and getting diluted and burnt.
Some of it is getting vacuumed up and blown into the exhaust.
And some might be going out the rear main seal.
But thats also assuming the pcv is hooked up.
Pull the plugs although im sure they are all pretty nasty.
But even with all that considered, thats a lot of oil.
look it over underneath front to back and look at the tailgate.
sometimes you can get a leak that kinda just mists everything with oil.
Hate to tell you this, but that is pretty awfull compression for 140k.
I think its never been maintained.
But do a leakdown test before you condemn it.
compression is only part of the story.
good luck

 

[RawbDidIt]

Forgot to mention for reference, mine is at 240k miles. I've got a new block torn down in the garage, about to rebuild it to go in.

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[thinger2]

Just noticed where you said you just got it.
When you are under it, look to see if it is suspiciously clean.
Like no dirt no grease clean.
It might have been pressure washed and you just arent seeing the leaks yet.

park it on cardboard from end to end and let it run till its nice and toasty and then shut it off overnight.
Dont know how much small block chevy experiance you have but pretty much if it aint leaking oil, it doesnt have any in it.

And like I said above, low compression numbers do not always mean your screwed.
Its not a good sign but stuck or burnt valves carbon loaded valves bad cam wrong cam stuck rings....
All kinds of things can cause low numbers.
Thats why the leakdown test is worth it.
It lets you make a more informed decision about the problem.

 

[PlayingWithTBI]

Dont know how much small block chevy experiance you have but pretty much if it aint leaking oil, it doesnt have any in it.

I don't know about that, it used to be true back in the old days with 2 piece seals and not using the "Right Stuff" in the right places. I go over 5000 miles and my dipstick still shows the same level as when I previously changed the oil. I use nothing but Mobil1 full synthetic oil. Yes, compression is very low. Did you try squirting some oil into the chamber through the spark plug hole and then see if your compression goes up? Look inside the exhaust pipe to see how much black soot there is. If it's sucking oil through the PCV valve, valve guides, and/or rings, it's going out the pipe. Time for a major repair/replacement.

 

[thinger2]

I don't know about that, it used to be true back in the old days with 2 piece seals and not using the "Right Stuff" in the right places. I go over 5000 miles and my dipstick still shows the same level as when I previously changed the oil. I use nothing but Mobil1 full synthetic oil. Yes, compression is very low. Did you try squirting some oil into the chamber through the spark plug hole and then see if your compression goes up? Look inside the exhaust pipe to see how much black soot there is. If it's sucking oil through the PCV valve, valve guides, and/or rings, it's going out the pipe. Time for a major repair/replacement.

Thats why the leakdown test is important. The oil in the rings trick can tell you if its blowing past the rings or going out the valves.
The best test is back off the rockers and put the oil in and listen to where the air is going.
It might be smoked. but, if its just an extreme oil leak. I would drive that thing till the rods came out of it.
Ive seen worse

 

[Postmech]

No smoke because of cats. That's low miles for worn rings on these unless they did not have air filter . I would change valve seals . Drain backs in head may also be clogged because no oil changes . Bad thermostat can cause oil to sludge, oil does not get warm enough to boil off condensation. Leaking intake gaskets can also sludge oil .

 

[smdk2500]

No smoke because of cats.

Your saying it isn't smoking because it has a catalytic converter?