I have had a problem with my 03 Maxima for about 18 months now.  It
started when I noticed a knocking noise about 2,000 miles after an oil
change when the engine was accelerating and at 1500-2000 RPM.  At
other speeds or when I was coasting or deceleratin, there was no
noise.  I figured out that I was low on oil; when I added oil (1-2
quarts, depending on how soon after the noise started that I added
it), the noise went away.  There are no visible leaks, no puddles
under the car, and no blue smoke in the exhaust.

About a year ago, the dealer determined that the loss was caused by my
short block (I'm no mechanic, so I'm going off memory), which they
replaced under warranty.  Since then, the problem has continued.  This
week, the dealer again looked the car over, did a compression test and
couldn't find a noticeable leak.  The one service manager said it was
normal for a car to lose 1-2 quarts of oil between changes (his Altima
does the same thing).

Again, I'm no mechanic, but I've never had a car that didn't have some
problem lose oil between changes.  If it did, it certainly didn't
knock like my Max.  Has anyone ever heard of this problem before,
especially in an '03 Max?  Is this normal?  Thanks.