A engine that is "burning oil" has several distinctive features to look for in determining the problem at hand. When you start a car from cold in the morning and see a cloud of bluish grey smoke emitted from the tail pipe it is usually a sign of bad valve guide seals or worn valve guides in the cylinder head. When idling at a traffic light and you gently move away and see blue grey smoke from the exhaust that too is valve guide wear or valve guide seals. If with an engine at operating temprature blue smoke is emitted from the tail pipe that is usually worn piston rings. Blue smoke all the time is a worn out engine.
It is important to determine the color of the exhaust smoke. Black emission is excess fuel, white smoke that smells slightly sweet, is usually a sign of a blown head gasket, blue /grey smoke is engine oil being burned by the engine.