Nissan Repair: Lot of Noise and vibration on cold start, timing chains, correct oil

Question
Hi, I have 96 Altima 110k. Recently, i have noticed that a cold start makes lot of engine noise and vibrations and after running for 5 mins (or keeping engine on in parking), the noise reduces and becomes normal. Also, noise reduces on cold start the moment you shift from Parking (P) to Drive (D). Putting it back to P again makes it. However, after 5 mins this shift does not make much difference. From last two oil changes, I have changed from conv 10W30 to Valvoline Max Life 5W30. This changed really improved the pickup.
Is it serious?. Pls help.

Answer
Amit,

5W30 is the correct oil to use for protection and power.  The tolerances in the engine lend themselves to thinner oil.  The noise you are experiencing?  Is it mechanical or a knocking?  Altima's have timing chains that get loose over the years and that can cause the noise on startup and then it takes a while to get things circulating and then it goes away.  Usually, the timing chain tensioner gets old and the chain gets stretched and that means a new chain and tensioner is in order.  If there is a scrubbing sound that means the chain is riding on the inside of the timing cover and that means you need to get it corrected soon.  Email me back with what kind of sound it is making and where it is coming from.