Power steering fluid is the hydraulic fluid in cars with hydraulic power-assisted steering. Three PSF families serve the Indian aftermarket: universal Dexron-class (red, for Maruti / Hyundai / Honda / Tata legacy), Pentosin CHF 11S (green, for VW / Audi / BMW / Volvo specific), and mineral hydraulic PSF (legacy Mercedes). Cannot be mixed. This guide gives the recommended universal Dexron-class BOM and Pentosin-equivalent route.
| Component | Function | % (m/m) | Indian Supplier |
|---|---|---|---|
| Group III 4 cSt base oil | Primary base, low pour, high VI | 80.0% | Reliance / SK / Neste via import |
| PAO 4 cSt | Low-temp boost | 3.0% | INEOS Durasyn |
| ATF DI light (reduced treat Lubrizol 9657) | AW + AO + CI package | 3.5% | Lubrizol India Mumbai |
| Friction modifier (reduced) | No clutch — minimal FM | 0.2% | Adeka Sakura-Lube |
| PMA VII + PPD (multifunctional) | VI improver + pour | 6.0% | Evonik Viscoplex 8-225 |
| Phenolic AO (2,6-DTBP) | Primary AO | 0.4% | BASF Irganox |
| Aminic AO (alkylated DPA) | Secondary AO synergist | 0.3% | LANXESS Naugalube 438L |
| ASA + thiadiazole CI | Ferrous + yellow-metal | 0.4% | King K-Corr + Vanderbilt 887 |
| Foam inhibitor (silicone) | Pump foam control | 200 ppm | Dow Corning DC200 |
| TMP-trioleate seal swell ester | NBR / HNBR seal compat | 4.0% | Croda Priolube |
| Red dye (ATF colour matching) | Industry-standard red PSF colour | 200 ppm | Clariant pigments |
| Group III diluent | KV / VI fine-tune | 2.18% | Group III |
| TOTAL | 100.0% | — | |
Process: blend Group III + PAO + seal swell ester at 65 °C; charge DI + FM + AO + CI; dose PMA VII slowly; foam inhibitor + dye last. QC: KV100 5.5-6.5 cSt, pour <-50 °C, foam D892 Seq I <25/0/0, seal compat per NBR/HNBR 168 hr at 80 °C (volume change <5%, tensile retention >85%). Ex-works cost ₹140-200 / L. Pack 1 L plastic bottle.
Power Steering Fluid is the hydraulic fluid inside the hydraulic-assist power steering system of cars and light commercial vehicles. The steering pump pressurises PSF; the pressurised fluid acts on the steering rack hydraulic cylinder to amplify the driver's steering input. Three PSF families: (1) ATF-like 'universal' Dexron-class — Mercedes 236.3, Honda PSF, most OEM aftermarket. (2) Pentosin CHF 11S green synthetic — VW / Audi / BMW / Volvo. (3) Mineral hydraulic PSF — older Mercedes.
Modern electric power steering (EPS) doesn't use fluid — large and growing share of new cars. Aftermarket PSF demand still strong for older hydraulic-PS vehicles. PSF is one product in our wider automotive lubricant formulation range, alongside dedicated EV fluid formulation work for the move to electric drivetrains.
Universal Dexron-class PSF BOM (%): Group III 4 cSt 80%, PAO 4 cSt 3%, ATF DI light 3.5%, FM reduced 0.2%, PMA VII + PPD 6%, phenolic AO 0.4%, aminic AO 0.3%, ASA + thiadiazole CI 0.4%, foam inhibitor 200 ppm, TMP-trioleate 4%, red dye 200 ppm, balance Group III.
KV100 5.5-6.5 cSt, foam D892 <25/0/0, pour <-50 °C, seal compat per NBR/HNBR test. The ATF DI and CI chemistry here draws on our additive package development work.
Pentosin CHF 11S is a synthetic ester / PAO-based PSF specified by VW Group (VW 52137, MB 343.0, BMW 81 22 9 407 758, Volvo). Distinguished by green colour, narrower viscosity tolerance, longer service life (lifetime fill in many VAG cars). NOT interchangeable with red Dexron-class PSF.
Mixing causes seal swell problems and pump damage. Workshop must identify which fluid the vehicle requires. CHF 11S costs 1.5-2x universal PSF. Indian VW Polo, Audi A4, BMW 3-series demand Pentosin specifically.
India PSF market driven by hydraulic-power-steering aftermarket — Maruti Suzuki, Hyundai, Tata, Mahindra, Honda. EV / electric PS conversion is shrinking the addressable market. Brands: Castrol PSF, Shell ATF / PSF, Total Quartz PSF, Mobil PSF, Pentosin CHF 11S, Liqui Moly, IOCL Servo PSF, BPCL Mak PSF, HPCL HP PSF.
₹180-450 / L retail (premium Pentosin higher). Lubechem custom universal Dexron-class PSF (LC-PSF-UNIV) ex-works ₹140-200/L; Pentosin-equivalent (LC-PSF-CHF) ex-works ₹240-340/L.
PSF circulates through hydraulic pump, hoses, rack seals — typically NBR or HNBR elastomers. PSF base oil and additives must not swell or shrink these seals. Too much swell — seal extrusion, leak. Too little swell — seal hardens, brittle, cracks, leak.
TMP-trioleate at 3-5% gives controlled seal swell — typically 2-5% volume change, 80-100% tensile retention after 168 hr at 80 °C. PCMO additive packages without seal-swell control attack seals quickly — using straight PCMO as PSF will cause seal failure within months. The same thermal-stability and seal-compatibility discipline carries across our specialty-fluid work, including heat transfer fluid formulation and turbine oil formulation.
Most OEM PSF is specified as lifetime-fill (no scheduled change). In practice, contamination, oxidation and seal degradation cause PSF to deteriorate over 80,000-1,20,000 km — visible as darkening, foaming, hard cold-start steering, whining pump noise.
Aftermarket service replaces PSF at 60,000-80,000 km as preventive maintenance. Service: drain old fluid through return line while engine running, refill with fresh PSF, bleed air. ~1-1.5 L PSF used per service. For workshops stocking the full hydraulic-fluid line, see our companion brake fluid formulation guide.
Share your target spec (universal Dexron / Pentosin CHF / mineral PSF), volume and pack format. We respond within one business day.