I'd put my money on this:

Nissan recommends 5W-30 because they sell Xterras from Florida (hot)as well as Alaska and Canada (cold). 5W-30 is good enough in hot climates, and necessary in cold climates. Personally, I've never seen a 0W-30 in a dino oil. Nissan would not recommend synthetic 0W-30 due to higher maintenance cost that they would have to publish.

Just my .02 cents.

That's more or less it - one oil from the factory makes it nice and easy. You got your hot and cold locales covered. It's available everywhere, and it's cheap.

Only higher-end, "performance" cars would suggest synthetic to their buyers... Who are usually in a higher bracket anyway and know they're gonna pay out the ass...

Which gas do you run.. Low octane fuel will cause the knock before the oil will. My money is on the fuel. I run only 93 octane and Castrol syntec 20W 50 oil. I am in the oil business so I do know what I am talking about to a degree

I still question how oil can cause knocking.

Lifter noise or other valvetrain issue, maybe.

What oil type to use is the least of your problems if your engine is truly "knocking" from an oil related issue rather than poor gas or ignition timing.

All motors have some sort of valve train noise, the Xterra just happens to be on the "louder" end of the scale.

I had a 1989 Mazda B2200 PU and it had alot of valve train noise (much worse than the X) and I put 200,000+ trouble free miles on that truck.

Kinda like, "takes a licking keeps on ticking ".
(I know bad pun)

You're right, I'm full of it and know absolutly nothing and spent my years in college getting loaded and taking basket weaving instead of fluid dynamics.

So ole wise one, spill it and let's crowd around the campfire and hear your technical discussion on which viscosity is best (give facts and backing reasons). And while you're at it, and since you don't agree w/ my resons on why Nissan recommends 5-30W, let's hear your reason on that one as well.
-Chris

thank uou everyone for your response, however i believe i was wrong in my assumption on the oil. I believe it's just cheap low octane gas. it's the wifes X and she has been filling it with 87. i still have what i believe is a pinging sound. i am planning on changing to 92 when this tank runs out, and see if it goes away.thanks for the info.

Err, that's what the X takes... Unless you've got a S/C, but it doesn't look like it.

I would try another gas station first.

Mine noise is definitely knocking. I have 900 miles on this oil change and the knocking is starting to be heard at idle. I will be changing the oil with 5w30 sync to see if that clears it up.
I have noticed no change with the different grades of gas even though that is an excellent point about ticking or pinging. The knocking starts around 1k miles on an oil change and I can't let it go pass 2.5k before it's just too loud.
The dealer said, what I mentioned before, that is was dirty oil and it needed changing even though the miles are not even close. They said that since I now drive a lot of rush hour, stop and go this is consider harsh and will dirty the oil quicker. :rolleyes:
Hello, thank you, try again. This is not the first vehicle I have own.

A much more correct answer would be that you used the wrong grade oil during a cold part of the year. Now change your oil correctly next time.

If you have excessive valvetrain noise, you might want to try dumping in a can of "Marvel Mystery Oil" along with the oil on your next oil change. That'll lube up the lifters, etc.

Geez, I posted this on the first page of the thread:
"Sounds to me like they are using the wrong term. Knocking (pinging, detonation) is usually linked to low octane gas or ignition timing setting. Valve lifter noise is a different issue and *can* be influenced by oil or even the filter choice.

dave and xtoy - so what is it?"

Is everyone taking stupid pills?

Dunno, but I think I mentioned it a few times myself... *shrug*

What oil filter do you use? That could be the culprit. Especially if it's a Fram oil filter, they're known for causing engine noise. Check out a Puralator or Mobil 1 filter.