After reading through an old post on the BITOG forum related to this report I was a little bit curious about a few things. At lunch today I pulled up the SAE J2360 specification for a little "light" reading. I believe that this is the current specification required for GL-5 certification, but I could be wrong on that. The test that interested me the most was the Copper Corrosion ASTM D-130 that showed a huge discrepancy between the Amsoil and the Lucas gear oils. Someone on the BITOG forum indicated that this test wasn't really applicable to gear oils as the additives were known to be corrosive for the "yellow metals" and that differentials don't really contain parts using those metals. I can't speak to what metals are in a differential, but it made me wonder if the Lucas gear oil is high in whatever additives are in play and the Amsoil has less of them (possibly uses different additives to do the same thing) then it's possible that the Lucas gear oil could be great in a differential application and not a good choice in a transmission. It's interesting that all of the oils tested were GL-5 certified which makes one wonder about why the Lucas and Royal Purple were so far outside the specification on a couple of the tests, both really lost a lot of their viscosity in the shear test. The result seems outside the box for what would be expected for a certified oil. I don't really know what to think about the results...
