Above is a Motul Gear 300 75W-90 UOA 'used oil analysis' report from a 2007 Nissan Pathfinder front differential (in Nissan Speak: 'front final drive') with 16,500 kms. Truck use is light duty no towing or roof rack use and driven normally at mainly city stop and go and freeway with about 8000 kms on this oil on ice and snow using 4x4. The front diff factory fill was dropped at about 4000 kms, replaced with a Pennzoil 80W-90 gear oil grade as requested in the owners manual and than at about 17,000 kms last fall I decided to put in the lighter Motul 75W-90 for winter use.

Problem though is the engineer doing the analysis doesn't like the silicon levels in the fluid and flagged it, but as a differential is a fairly closed system I'm wondering if the high silicon levels may be coming from seals rather than dirt. The Nissan manual recommends in numerous places to make sure to use only a 80W-90 or 90W at high ambient temperatures in the front hypoid differentials in these trucks, but this 75W-90 appears to be doing it's work I think. Any comments appreciated.

Here's an analysis of the same Motul Gear 300 75W-90 currently in the truck although the VOA was taken from the used bottle which had been in the shop for a few months, dirt must have got in during filling the differential;



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