Why is 1998 Chevy Metro losing oil It smokes only on ignition. I can smell burning oil under the hood. There are 161000 miles on the car. Car runs great.?

Why is 1998 Chevy Metro losing oil It smokes only on ignition. I can smell burning oil under the hood. There are 161000 miles on the car. Car runs great.?
Maybe valve cover gaskets are leaking
Could be burning oil, but catalytic converter burns so hot (normal) that smoke is dissapated prior to being observed at the tailpipe