Historically, my MR2 had been using a little less than 1qt. every 1000 miles (JUST barely within factory spec.).  We finally figured out it was the valve cover gasket and the sparkplug seals that were leaking...  After that, had the oil changed, and on the drive home the dipstick blew out, spraying the engine bay with oil.  Apparently the oil change tech forgot to push it all the way down.  Luckily I decided to check after smelling a suspicious whiff of oil!  Only lost enough oil that the level came down to the "full" line instead of being the little ways above the full line that it usually is after an oil change.  Proceeded to put 1300 miles on the car (mostly city, but a couple of 1+ hr. highway trips as well) over the next couple of months and the level never dropped.

Yesterday I ran down to (and back from) near Cincinnati to see some friends for a few hours.  Roughly 400 mile round trip (aka, 11 gallons or $45 of gas :-)  ).  Checked the oil this morning and it looked to be about .3qt below the full line!  No apparent oil leaks, no smell of oil at all.  I expect the engine to burn *some* (it's a bored out rebuilt motor (due to failed oil pump at 180k miles that caused deep scarring of all 4 cylinders) that the factory designed for regular oil, but I'm using a full synthetic in now instead (to avoid the sludge buildup that killed the motor the first time around)) and I actually found it disturbing to NOT have to add any the first 1300 miles.

My only thought is that the first 1300 worth of trips were not long enough to really heat the thing up and burn off the condensation.   Perhaps I had significant amounts of condensation that had formed and replaced the normal missing oil.  When I checked the oil before the trip, there was that nasty yellow whipped cream looking stuff in the oil cap, so I know there was at least some condensation in the system...  Even just 1 qt. low on a Toyota 5S-FE can lead to a spun bearing, so I'll be keeping a real close eye on it.