KIA OPTIMA ENGINE BURNING OIL

It Come Out White Smoke When The Oil Is Low. Took It To Two Mechanics No Leak, Change Pcv Valve And Did A Tune Up. Do Not Know What To Do...

2008 Kia Optima 6 Cyl Automatic 10,000 Miles Oil Light Came On. Dip Stick Showed Oil Level On The "l" Mark (low) I Never Added Any...