I would suspect piston rings.  Because you don't find oil marks under it,
the oil is probably being drawn into the cylinders and spent out the
exhaust.  There may be another source for the oil to leak into the
cylinders.  For example another car of mine is known to have a problem
developing a leak between the intake manifold and the internals of the
engine so that the oil gets sucked into the mainfold.  Sorry, I can't offer
you more, I hope this helps is some way.

Hi Everyone,

I have a 1998 Isuzu Trooper that's been going through a lot of oil
lately.  It has about 98,000 miles on it on a rebuilt engine.  I just
recently got an oil change on it about 1200 miles ago.  There's no
apparent leak as I can't spot any oil spots underneath the Trooper
after I've parked it for an extended period.  I'd say it goes through
about 5 quarts every 600 miles.  What could be causing this?  Does an
older engine just burn up that much oil?

On a related note, I was visiting a friend over the weekend and on the
return trip the Oil Warning light came on after I drove over a long
incline.  The engine started losing power and felt like it was going
to seize up.  I took the next exit and made it slowly to a gas
station.  I popped the hood and checked the oil level.  Bone dry.  I
bought 5 quarts of oil and filled it up.  We let it sit for about 10
minutes and I turned the engine over.  It sounded like it was idling
fine.  We let it run for about 20 minutes.  I tried revving the engine
up gradually.  When I passed about 1200 RPMs I could detect a mid-
range rattling sound coming from the engine.  We tried driving around
the parking lot and then proceeded out to the local street for some
testing.  Other than the noise it didn't seem like it was losing any
power.  We got back on the freeway and made it back home slowly.  By
the time we made it back 35 miles the rattling sound was significantly
louder.  I tried turning over the engine today and it's making that
rattling sound.  ie.  TAT-TAT-TAT-TAT-TAT-TAT-TAT.  Does this mean I
have a busted rod in one of the cylinders?

TIA!

-Peter