As my signature says I have a 95 that I just changed the rear diff fluid in. I was planning on putting Schaeffer's 70W-90 in; but, my auto parts store didn't have enough so I ended up using Castrol 70W-90 synthetic. It is a daily driver that doesn't get many miles and only seldom pulls. When it does pull it pulls a small horse trailer for long trips and is usually in the mountains with some heavy grades and associated hard pulls. This is probably similar to a lot of folks use I would imagine.

I have been reading quite a few threads here that seem to think that using a 70W-140 is preferable to a 70W-90 when going with synthetic. What do you guys think?

HL

 

70W-140 is great if you tow heavy in the summer but is sluggish if it gets cold where you live. I ran Schaeffer's 70w140 semi-syn one winter, whenever the temp dropped below 20F the truck would barely coast when cold. Maybe the full syn would be better but if you don't tow there is no reason to use 140.