AFAIK, Fuser Oil 2 has 1-2% more silicone or something in it. Fuser Oil 2 is supposed to extend the life of the Fuser Roll.
Also, in order to switch from 2 to 1, the Reservoir needs to be swapped out and the system needs to be drained and cleaned. This requires a service call and I was told that they will only do it once.