I can totally understand that!
As far as the oil, I have no real loyalty to Amsoil. I got a great deal on a case so I tried it. I can say that when I check the dipstick (ARB Dif Cover) the oil still looks and smells like new even after 52,000 miles. Most of the general 4x4 shops I have asked say they just use the cheapest dif oil they can find because they have the covers off all the time, but If you are going to use the oil for more mileage, use synthetic.