Could just be a vacuum pump problem or vacuum leak. It exhausts into the crankcase and if it's pumping lots of air in there it carries enough oil out the blowby tube to cause very high consumption.
My '96 did a weird thing about 2-1/2 years ago, it went through a phase for a few months where it would use 2-3 quarts of oil in just a few hundred miles, and I had oil all over the tailgate and coating the bottom of the truck. I ended up changing the oil and using a good dose of engine flush. After that oil consumption went down dramatically. Never really figured out what was up. I had about 365k on it then. Now at 405,000 it uses about 1 quart every 1000 miles, and doesn't blow much out the tube.