My 2005 G35X has logged about 43000 miles. I changed the front (the x has a front diff as well as a rear.) and the rear fluids. I used Redline 75-90 gear oil in both the front and rear.
The old oil looked new as it was pouring out. The magnet had very little metal fillings attached.
Now I admit I am no automotive expert but in my opinion I really question the need for the differential oil change. I fell that I wasted my time and money. Has anyone had a similar experience? Any professionals here; how do you feel?
CliffordS

 

I just changed the rear diff oil in my 04 G Sedan. It has 81k miles. My fluid smelled horrible and was full of shavings. In addition my plug magnet was probably 1/8 inch thick of shavings. I wouldn't say it was a waste. Probably a good idea to get some better fluid in there early to prevent lots of wear. I went with the Lucas Oil 80W-90 in mine.