1989 Chevy S-10 Using about a quart of oil in less than 100

My son has a 1989 Chevy S10 with a 4 cyl engine. The problem is that he is going through a quart of oil every 80 to 100 miles. There is no smoke from the exhaust and I have had the valve seals replaced. I have also checked the PCV valve and it is clear. We did and oil change at the beginning of summer and the oil was black in less than 200 miles. I should note that we bought the truck earlier this year and it had set for about 4 months before that. A mechanic friend said he thought it might be the oil rings. Compression is good about 128. I do notice that black soot or condensation blows onto the ground from the tailpipe at startup. But no smoke whatsoever.