A bad head gasket *can* leak oil externally but it doesn't always. The blowout into the timing chain cavity is not uncommon, but is often accompanied by massive smoke while driving and poor power. The equally pooc compression on all cylinders leads me to believe either the test was done cold (shame on the techs), or you've got a bunch of ovaled cylinder walls and a short block that's toast. A good 603 uses very little oil, mine is also about 6000 miles per quart. I wish I could say that your problem was a bad head gasket but I very seriously doubt it...