Definition: A silicon or petroleum based lubricant, shock oil is used inside the cylinder of an oil-filled shock.
Shock oil comes in different weights such as 40, 70, or 100. Ask your hobby shop sales associate for recommendations based on your car/truck and the conditions under which you run it. Changing the weight of the oil changes the damping rate -- the compression of the shock -- so that you can finetune it for different road or track conditions.