What Is Power Steering Fluid?
Power steering fluid is a hydraulic fluid used in vehicles equipped with hydraulic power steering (HPS) systems. It is pressurised by the power steering pump — driven by the engine via the serpentine belt — and fed to the steering rack or steering box, where it provides the assistance force that makes turning the wheel feel light and effortless.
Without power steering assist, most modern cars (especially SUVs, utes, and vans) would require considerable effort to steer, particularly at low speeds and in car parks.
Hydraulic vs Electric Power Steering
Many vehicles sold in NZ since approximately 2010–2015 use Electric Power Steering (EPS), which uses an electric motor attached to the steering column or rack rather than hydraulic pressure. EPS vehicles have no power steering fluid — there is no reservoir to check. Common NZ models with EPS include newer Toyota Corollas (post-2014), most Mazda Demios (post-2012), and most modern Honda Jazz models.
If your vehicle has a "PS" reservoir under the bonnet — usually a small transparent or opaque bottle near the power steering pump — it uses hydraulic power steering and requires fluid maintenance.
What Power Steering Fluid Does
- Acts as a hydraulic medium to transfer pump pressure to the rack.
- Lubricates the pump, rack seals, and hose connections.
- Protects against corrosion and wear in the pump and rack.
Signs of Low or Degraded Power Steering Fluid
- Whining or groaning noise when turning the steering wheel — particularly at full lock or when parking. This is often the pump cavitating due to low fluid.
- Heavy or stiff steering — especially at low speeds.
- Steering feels jerky or inconsistent.
- Visible fluid leak — look for reddish, amber, or clear oily spots under the car near the front. Power steering fluid can leak from the pump, rack seals, hoses, or connections.
- Discoloured fluid — healthy fluid is clear to pale amber or red; dark brown or black fluid is degraded and should be changed.
Common Fluid Types
Most vehicles use either automatic transmission fluid (ATF) (often Dexron or equivalent) or a dedicated power steering fluid. Using the wrong type can damage pump seals. Always check the reservoir cap or owner's manual — it will specify the correct fluid type.
Do not use brake fluid, engine oil, or any other hydraulic fluid as a substitute. These will damage the seals.
How Often to Change It?
Power steering fluid change intervals are often neglected — many vehicles don't have a specified interval. A common recommendation is to check the fluid annually and flush the system every 3–5 years or if the fluid has darkened significantly. Many independent NZ workshops recommend doing it whenever the power steering pump or rack seals are replaced.
NZ Costs
| Service | Typical NZ Cost |
|---|---|
| Power steering fluid top-up | $20–$50 including fluid |
| Power steering fluid flush | $80–$160 |
| Power steering pump replacement | $350–$700 all-in |
| Steering rack seal kit/replacement | $400–$900+ |
Fluid leaks from the steering rack are common on older Japanese imports; if left unaddressed, the rack itself will eventually need replacing — a much costlier repair.
WoF Implications
WoF inspectors check steering for play, binding, and abnormal noise. A power steering rack that's leaking fluid or a pump that's groaning and underperforming may attract attention during the inspection. Heavy or vague steering can result in a WoF failure.
When to Book a Mechanic
- You hear whining or groaning when turning.
- Steering has become noticeably heavier.
- You can see reddish or oily spots under the front of the car.
- The fluid reservoir is visibly low or the fluid is black.