Use GM Power Steering fluid, or its equivalent.
FLUID LEVEL CHECK
See Figures 1, 2 and 3
Check the dipstick in the pump reservoir when the fluid is at operating temperature. The fluid should be between the HOT and COLD marks. If the fluid is at room temperature, the fluid should be between the ADD and COLD marks. The fluid does not require periodic changing.
On systems with a remote reservoir, the level should be maintained approximately 1 / 2 -1 in. (13-25mm) from the top with the wheels in the full left turn position.