Power Steering Fluid

Power steering fluid acts as the "lifeblood" of a Hydraulic Power Steering (HPS) system. It serves as the hydraulic medium to transfer power from the power steering pump to the steering rack, whilst providing vital lubrication to internal valves, cooling the system, and protecting against corrosion.

Note: Only vehicles equipped with hydraulic or electro-hydraulic power steering systems require power steering fluid. If your vehicle uses Electric Power Steering (EPS), never add any fluid to the steering system.

Why Does It Need Changing?

Even though the power steering system operates as a closed loop, the fluid inevitably degrades over time: 

Thermal Breakdown: High operating temperatures generated by continuous pressure cycles and pump friction cause the fluid to oxidise, darken, and lose its lubricating properties over prolonged use.

Wear and Tear Debris: The steering pump and steering rack internals produce microscopic metal particles during operation. If these contaminants are not flushed out with the old fluid, they accelerate wear and can even clog the steering control valves. 

Seal Deterioration: Aged, degraded fluid turns acidic, accelerating the wear and hardening of rubber seals and oil seals, which eventually causes steering rack leaks.

Signs It Is Time for a Change

Always refer to your vehicle's service handbook (typically every 40,000 to 60,000 km or 2 to 3 years). Have the system checked immediately if you notice any of the following symptoms: 

Discoloured Fluid: Fresh fluid is typically clear red or translucent amber. If it turns dark brown or black, or emits a burnt odour, the fluid is severely degraded. 

Whining or Whirring Noise: A whining sound when turning the steering wheel often indicates reduced fluid viscosity or aeration/cavitation in the steering pump caused by contaminants. 

Heavy Steering: A noticeable increase in steering effort or erratic hydraulic assist, usually caused by compromised fluid viscosity. 

Choosing the Right Fluid

Never assume one fluid fits all! Different vehicle manufacturers specify distinct fluid characteristics such as viscosity, anti-foaming properties, and friction modifiers:

ATF (Automatic Transmission Fluid): Many older hydraulic setups run on standard ATF (such as Dexron ratings). 

Dedicated Power Steering Fluid (PSF): Many European and Japanese makes (such as Volkswagen, Honda, and Toyota) specify dedicated mineral or synthetic hydraulic fluids (such as OEM-specific PSF or CHF specifications). 

Never Mix Fluids: Never top up or mix different fluid types or brands together! Incompatible additives can cause seal swelling, seal failure, or sludge build-up.

Maintenance and Top-Up Tips 

Fluid Level Inspection: Check the reservoir level (MIN/MAX markings) when the engine is cold. If the level drops below MIN, top it up promptly and inspect the system thoroughly for leaks. 

Flushing Methods:

Full System Flush (Return Line Method): Disconnecting the return hose to purge old fluid while continuously topping up with fresh fluid until clean fluid emerges. This is the most thorough method. 

Siphon & Refill Method: Using a syringe or fluid extractor to empty the reservoir, refilling with fresh fluid, and turning the steering lock-to-lock to circulate before repeating. While simpler, it does not completely clear the fluid trapped within the steering lines.

Contamination Prevention: Always clean the reservoir cap and surrounding area before opening to prevent dirt, grit, or moisture from entering the system.

What If You Use the Wrong Fluid?

Adding the wrong fluid specification can quickly damage internal rubber seals (causing them to soften, swell, or disintegrate), resulting in severe leaks that often require a full steering rack overhaul. If the wrong fluid is added, visit a reputable workshop immediately for a complete system flush and fluid replacement.