Most vehicles on the road today are equipped with some form of power-assisted steering. Without power steering, the sheer weight of your car, truck, or SUV would make it very difficult to turn the steering wheel. That is especially true when your vehicle is standing still, or when you are parking.
Although the automotive industry is beginning to see many late-model vehicles that feature electric-assist power steering systems, still the majority rely on hydraulic power. The oil in these hydraulic systems, known simply as power steering fluid, is used to transfer power in order to assist the driver in turning the steering wheel with ease. It also serves to lubricate and cool the system. A power steering fluid change is a service aimed at emptying out all of the old power steering fluid and replacing it with new as part of routine vehicle maintenance.