green antifreeze in my 93 civic

Never did it.

I have been keeping extremely close observation of my oil consumption
over the last year or so. Excessive oil consumption was the primary
reason I was considering an engine replacement, so I wanted to perform a
rigorously controlled study of just what was getting sucked though the
motor.

Well.

It's been roughly 1,500 miles per quart for a long time (I determine
this after correcting for an earlier error in interpreting dipstick
markings).

Very lately consumption has been DECREASING.

In November it was 1,500 mi/qt.
In December it was 1,800 mi/qt.

I just checked it now, the proverbial bell having rung to indicate it
was time for another reading. I checked, then checked again. And again.
I even went pessimistic on my dipstick reading.
It's 2,500 mi/qt. At least.

I do not know what's going on here. Each year there is a decrease
corresponding to the winter drop in ambient temperatures, but this is
the most consumption has declined in several years. And this has not
been a particularly cold winter.

Some time ago I posted a query to rec.autos.tech about this, and it was
suggested to me that I probably had a collapsed oil control ring spacer.
In such a case, there would be sudden increase in oil usage, then the
piston groove would eventually carbon up and usage would decline. Maybe
this is the explanation.

Without having X-Ray vision and being able to see inside the engine,
this is a real mystery,

 

you've changed oil though haven't you? my 89 civic used to burn regular
oil but that's dropped dramatically using mobil 1. and it continues to
drop too.

i have two theories.

1. there's less volatile fraction in the base oil of m1 to evaporate.
[regular oil is a mix of weights. the light ones are easier to boil off.]

2. i read about piston aero engine oil not having viscosity modifiers
because they tend to ash around the piston rings. if this is the case,
and m1 is proving to be a very effective cleaner of my previously
resined up engine, i can see it getting rid of piston ring deposits
allowing them to seal better again.

i'm basing 1 on what i know to be fact about the mix and basic
chemistry. 2, i'm guessing, but i don't buy the collapsed ring spacer -
that would make consumption go to heck, and it wouldn't start to seal
after time - it would just continue to deteriorate.

but for sure, my experience of m1 is the same as yours.

 

could be just plain old chemistry. oil contains various 'seal
swellers' and undoubtedly every brand has its own concoction, maybe
the brew in Mobil 1 just happens to suit what your engine needs better
than other brands. just handwaving here, but given mobil 1's ability
to creep and leak, could be they even put in a more powerful sweller
to keep things under control, relying on the increased lubrication of
the oil to keep the seals from wearing more when swelled.

 

well, even 1500 miles isn't too bad. i'm going through a quart of oil
every gas fillup or two, but that's just because my vtec solenoid is
spraying oil like a texas gusher.