You need to figure out the oil is entering the combustion chamber from bottom through piston rings or from the top through the head,
If the smoke only during the cold start after vehicle is sitting for long time, then it's the time for valve job, could to get the valve job done, replace the valve oil seals and get the seating done.
But if the smoke is emitting continuously even when engine is hot then as pointed out in above post it could piston rings.
Also keep an eye on the coolant level aswell every 1000kms along with oil level, to see if coolant is also getting burnt or not along with oil.



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