'Cold' start noise-
 

I don't get here often, but thought I'd post this: My wife has an '05 summer driver that has had only a battery, tires and fluid changes over 58k miles. I've used Rotella T6 5-40 with a Nissan filter and changed each fall before sleeping away the winter. Last fall I was out of T6 and used Mobil 1 0-40. About a month ago we noticed a strange quick 'shnick' type sound at the first morning cold (well 70 degrees) startup. I was thinking timing chain/tensioner a likely source and decided to do this years oil change a bit early and back to T6 oil. The result is that over the last few weeks the sound has disappeared. I figure oil pressure bleed down over night and maybe no ratchet effect parts working? Maybe 4-5k miles was too much for the Mobil 0-40??=hard for me to say.

Its the oil pressure driven timing chain tensioner. The chain gets slack, then hits the cover till the pressure increases. Whenever you do the major tune up, think its at around 120k, change the tensioner and the chain guides and you will be set. Its a common problem, but its nothing to worry about atm. If it gets enough slack to make the cam and crank get off from each other, the sensors wont allow the engine to start. Hope this helps!

Could be the starter. The solenoid isn't retracting fast enough, causing the grind.

Why are you using a motor oil designed for diesel engines on your Z?

Wiki for Rotella motor oil:
"However, it [Rotella] is formulated specifically for vehicles without catalytic converters, containing phosphorus levels beyond the 600-800ppm range. Therefore, Rotella is not recommended for gasoline vehicles with catalytic converters due to the higher risk of damaging these emission controls"

Was kind of wondering the same...

As said before, timing chain rattle most likely. Many Nissan's have it and live with it indefinitely.

Howdy again-I like a robust oil and also use Rotella 'diesel' oils in some older 60s-70s-80s cars. My '85 El Camino has 160k miles on the orig cat and all is well. I also never experienced any particular valve issues when leaded fuels went away or have suffered any of the 10% 'gasohol' panic outcomes. Factory and govt recommendations are a guide for me, but not the final word. I have built and repaired a number of engines over the years and thin and sheared oils are a larger concern to me.The timing chain setups on dual overhead cam V engines are pretty' busy' and I also like the T6 oil for these. The public doesn't care much for having to time change belts any more even while they do a nice job in shock damping of valvetrains. I rather prefer the push rod engines but glad to hear that the Nissan chain setups can carry on even if the wife didn't like hearing it. Thanks

The main chain tension-er sometimes doesn't see oil pressure immediately so it can cause the chain to sound a little slack and slap on the insides of the covers. Not really a big deal at all.

If the chain slipped, you'd know very quickly. Like... Instantly as the engine would basically crap it's self.

If you want to run whatever oil, and not worry about the emissions, look into installing a catch can. Any z owner should consider doing this regardless of oil use/mileage as crank case vapor really builds up in the intake and robs you of power/makes the car run less optimally.

TIL people thought Sentras were the tits.

Engine light from catch can
 

I installed a catch can and it tripped a engine light so I removed it.