high oil consumption with only 80k

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Old 05 Sep 2005, 11:24 pm   #1 (permalink)
George
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Default high oil consumption with only 80k

OK, not a camry, but a close relative. I have a 2000 corolla that is using
about 1 quart per 1000 miles. No leaks,
definitely coming out the tailpipe, back bumper has residue above tailpipe
and tailpipe is black. Does not smoke on start up and I only see smoke when
accelerating hard. Cylinder compression is all with 5 psi of 185, plugs are
not fouled. 82,000 miles, regular oil changes. Is it possible for this
much consumption from valve stems seals, any other possibities other than
rings? I also have a 96 camry with over 200k that was maintained same way
with no oil use at all. Thanks



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Old 06 Sep 2005, 07:48 am   #2 (permalink)
C. E. White
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Default Re: high oil consumption with only 80k


"George" <gpuzen@bellsouth.net> wrote in message
news:XP8Te.690$bC3.510@bignews1.bellsouth.net...
> OK, not a camry, but a close relative. I have a 2000 corolla that is

using
> about 1 quart per 1000 miles. No leaks,
> definitely coming out the tailpipe, back bumper has residue above tailpipe
> and tailpipe is black. Does not smoke on start up and I only see smoke

when
> accelerating hard. Cylinder compression is all with 5 psi of 185, plugs

are
> not fouled. 82,000 miles, regular oil changes. Is it possible for this
> much consumption from valve stems seals, any other possibities other than
> rings? I also have a 96 camry with over 200k that was maintained same way
> with no oil use at all. Thanks


Assuming your catalytic converter is still working, it will take care of the
oil smoke once the car is warmed up. Do you get any blue or blue-gray smoke
for a short time after a cold start? A black tailpipe is normal these days.
1 quart in 1000 miles is not all that bad. I don't know what Toyota claims
is acceptable, but I am confident GM would say that is OK (but I would not
be happy - it has been a long time since I had any car that used 1 quart of
oil in a 1000 miles, and it was British). Howver, all car consume some oil.
There is always a thin film left on the cylinder walls on each power stroke
and at least some of this is consumed. Consider this:

I think everyone can agree that even the best oil control rings in the world
must leave a thin coating of oil on the cylinder walls. They have to or the
oil control rings would not be lubricated. Likewise the compression rings
would be running dry and would quickly wear out. How thin do you think this
layer would be? Maybe .0000003"? This is really thin, a single oil molecule
is around 0.0000003" in diameter. A 1.8l Corolla engine has a 3.11" bore and
a 3.60" stroke. This means that there is a cylinder wall surface area
exposed to the incoming charge of 3.11" x 3.1412 x 3.60" x 4 = 141 sq. in.
The total volume of oil needed to cover this area is perhaps 0.000042 cubic
inches. I think everyone can agree that at least some of this oil is
vaporized and consumed on the power stroke. For simplicity, we will assume
that one half is consumed on the power stroke and none is lost on the
exhaust, intake and compression strokes (this seems like a really
conservative assumption to me). So, this means that around one fourth of the
oil coating the cylinder walls is consumed for each revolution of the
crankshaft, or around .0000011 cubic inches per engine revolution. To
simplify things further, assume we only drive around in the top gear and
never let the car just idle (again, a conservative assumption). For every
mile, the engine will turn over around 3000 times. So for each mile the
engine should consume around 3000 x 0.0000011 cubic inches of oil. This is
..03 cubic inches of oil. In 1000 miles, this is 30 cubic inches of oil. 30
cubic inches of oil is roughly 0.6 quarts!

So you say - BS! Lots of engines don't use as much as 1/2 quarts of oil in
three thousand miles. I agree, so where did I go wrong? Maybe the thickness
of oil film is too thick. Cut it in half, so now you only use 0.3 quarts in
1000 miles (oil molecules aren't this thin by the way). Maybe only 10% of
the oil is consumed (not 25% as I assumed), so now you only use 0.1 quarts
in 1,000 miles. No matter how you cut it, your engine is burring some oil.
And this doesn't include oil lost when you are idling (particularly when the
engine is cold), or oil lost down valve seals (and you have 16 of those), or
though the crankshaft seals, or through leaky gaskets, or by evaporation, or
through the PCV system (look in the PCV valve and lines sometime...there is
oil in there on its way to the intake to be consumed).

So why do so many people claim their engine use no oil. One reason -
blow-by. Blow-by past the rings adds material to the oil in the crankcase.
Some of this stuff evaporates and is consumed via the PCV system, but other
components of blow-by stay in the oil (why do you think oil turns black?).
We used to have an old tractor that actually "made" oil between changes - as
long as you did not work it too hard. It you do a lot of in-town driving and
never really get the oil hot, a lot of contamination can collect in the oil
pan (unburned hydrocarbons, water, etc). This crap can make it seem if you
are using very little oil around town. But then, when you take a long trip
and get the oil hot, most of this stuff will evaporate and be sucked into
the engine via the PCV system and burned. With the crap removed, it looks
like you had a sudden increase in oil consumption. In reality you did not.

Read the following references:

http://www.pzlqs.com/Tech/Bulletin/Q...al/pdf/g08.pdf
http://www.pzlqs.com/Tech/Bulletin/D...l/pdf/g01b.pdf
http://www.pzlqs.com/Tech/Bulletin/Q...al/pdf/g11.pdf

I would not be thrilled if my car was apparently using 1 quart of oil in
1000 miles. However, I would not push the panic button either. Unless you
get a steady increase, I'd suggest you just drive the car and keep the oil
checked. I would suggest you have the PCV valve replaced and make sure there
are no small leaks. As the Quaker State bulletin above points out, a very
small leak can lead to significant oil loss. Not all leaks show up on the
driveway. Some engines only leak when running and the leaks can be hard to
find. Look for oil spots on the engine or under carriage. Particularly check
at the bottom of the bell housing.

Ed



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Old 06 Sep 2005, 02:35 pm   #3 (permalink)
Daniel
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Default Re: high oil consumption with only 80k

check auto-rx.com

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