DSI Alpha-1 Fluid is an ultra-pure, ultra-clean fire resistant insulating oil.  It's a one-step retrofill solution to upgrading the fire resistance of standard mineral oil transformers.  It's an excellent choice for original fill for transformers, especially those that will be placed in very cold or very hot environments.  It's made from the same type of synthetic hydrocarbon oils that are used to make synthetic motor oils.  Alpha-1 is compatible with standard transformer oil, with PCB fluids, with Beta or R-Temp fluid, and with vegetable fluids.

Alpha-1 Fluid is listed by Factory Mutual for use in transformers located indoors. 

Made and used since 1992, there are thousands of transformers worldwide that are filled with Alpha-1 Fluid.  Testing shows that the fluid in even the oldest of these units hasn't changed, darkened, or oxidized. Because of its low viscosity, Alpha-1 cools transformers better than other fire resistant oils.  Transformers that were designed for standard transformer oil will not need to be de-rated when retrofilled with Alpha-1 Fluid. Alpha-1 pours at temperatures down to -55 C.  It's ideal for applications in cold environments, or when a full-load cold start is a possibility. Being synthetic, Alpha-1 contains no sulfur at all.