I know that someone has used it. I need to know if 50W oil is safe for the V6 engine. Im getting my oil changed from 10 W 30 to about a 20 W 50. The X has 10,300 miles on it.

The question would be why? The Xterra is designed to run on 5W/30 or 10W/30 and you will not see any benefit by using a thicker oil, not that Nissan really could ever find out but if you had an engine problem they probably would not warranty it.

Ive been told by Nissan Frontier owners that have the same engine as the X, that the 50W oil makes a noticeble change in the way the engine handles, for the better.

The engine handles? If anything you might lose power, the thicker oil will cause more resistance on the moving parts. I have had Nissan trucks for 14 years now and I have never used an oil that was not recommended by Nissan, my 88 Pathfinder(my friend owns it now) has over 250,000 miles on it and does not burn a drop of oil...proper maintenance and using quality/correct parts is the key.

Thanks for the info man, looks like ill stick to 10 W30, now for another question, I use Castrol GTX, can I switch to Mobil 1 safely? Or, what would you reccomend.

Why in the hell would you even consider going against Nissan's specification, especially that far outside it, and on such a young engine?

Not only will 50W oil increase drag on the engine, it will increase your oil pressure and could blow an engine seal. Not to mention it won't flow as readily into the galleries and parts of your engine would not receive sufficient lubrication.

As for going to Mobil 1, you can switch between any oil you please at any time. Go for it.

Brent

I already stated that I want going to do it, but thanks for your advice though. Good, glad I can switch to Mobil 1.

I knew you had already decided against it, but I still question your reasoning for considering it. Also wanted to mention other reasons why it's a bad idea as an FYI.

Brent

I run 0-30W. 50W is a baaad idea, but you know that now.
-Chris

Oil??? I am at a loss.. So much information. I followed the break-in manual fairly close, switched over to Mobil 1 at 9K changed every 3K following and MY engine went at 47K I think using 5W 30 this time around is in the cards, used 10W 30 last time. Nissan is replacing my engine under warranty (short block) Problem is, no head gasket sets available to finish the job. (Three weeks and counting) Anyone seen these things?? Let me know. My dealer say's Nissan is just not making enough replacement parts.

RJ

What went south in the motor, bearings? Just curious. The specific area in the motor going bad will often tell you what caused the problem. Try Courtesy on the gasket set. You might try getting a gasket set from a parts supplier locally also. The warranty, if you have one still, might not apply if you use other than Nissan gaskets though. Good luck on the R/R.

Charlie