tester1ca
New member
I own a 2013 Sierra 2500 WT with the gas 6.0. It's only got 50,000 kms [30,000 miles] on it and I thought that I would change the rear diff fluid. The manual calls for 75w90 synthetic. I have been searching online for a quality lube and have been blown away by all the tests done on different lubes available. So many choices of good name products but each one isn't as good as the other and people say don't use this one or only use that one. I ended up getting a deal on some Amsoil Severe Gear. But, here is my issue. It was 75w140 and the person selling it to me said it would be fine even though the manual said to use 75w90. I ended up putting it in this morning and I'm now wondering whether to go back to a 75w90 in the fall before the winter as I'm not sure it will be OK in the freezing temps. I tow a small 5th wheel in the summer months so I think 75w140 will be fine through the hot weather but I'm weary of the cold days. What do you think?