My 1999 Sonoma, manual 2.2 liter 4 cyl with 130,000 miles, uses (or loses) up to a quart of oil in two weeks. The oil pressure maintains a steady 60 PSI and the exhaust is clear, even when starting. That would seem to indicate that ring wear is not the problem. I put a big piece of cardboard under the truck over the weekend, no drips. The oil pan is dry, and I see no sign of leaks. After doing a number of googles, I read suggestions about replacing the valve guide seals (seems like major surgery) and switching from 5W-30 to 10W-40 or 20W-30. The truck is driven 300-400 miles a week on the Interstate in a moderate climate (Seattle area). Any suggestions?