2013 Nissan Altima smoke upon start

My car has a lot of smoke as soon as you start the engine then goes away, bluish color. Is it due to oil sludge? The mechanic said just excess oil burning and will go away but never did. Now he said from oil sludge? This happened after we brought in the car for the recalls to the dealer.

Are you checking your oil level on a regular basis? Is the level dropping? by how much?

How many miles on this car?

Recalls? which ones?

Does it happen when the car has been sitting several hours or overnight or longer?

Does it happen to the same extent when the car is restarted after a short shutdown?

The most common cause for blue smoke out the exhaust when an engine is first started is, leaking valve guide seals.

If this started right after the dealer did the recall service, call the dealer and ask what the recall service involved.