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Hydraulic Fluids

Fire-resistant PAG hydraulic fluids delivering safety, thermal stability, and reliable performance in high-pressure industrial and mobile hydraulic systems.

Performance Advantages

Why PAG for Hydraulic Fluids

Inherent fire resistance

Water-glycol and anhydrous PAG fluids provide fire-resistant properties without compromising lubrication performance, critical in steel mills, foundries, and mining applications.

High viscosity index (VI > 200)

Maintains hydraulic response across wide temperature ranges, ensuring consistent system performance from cold starts to high-temperature operation.

Excellent shear stability

PAGs resist mechanical shear degradation, maintaining viscosity and system pressure in high-pressure, high-cycle hydraulic systems.

Low compressibility

Consistent hydraulic response and precise control in servo-valve and proportional-valve applications.

Application Segments

Sub-Segments

Fire-Resistant Systems

Steel mills, foundries, mining; ISO VG 46–68; water-glycol formulations (HFC category per ISO 12922).

Product Range

Recommended PAG Grades

Typical grades for hydraulic fluids: PAG 32, PAG 46, PAG 68

AntioxidantsBase Fluid Additives

Aminic Antioxidant SPDA

Treat Rate: 0.3–0.8% in grease

High-temperature antioxidant for chain greases, bearing greases, and high-temperature specialty greases. LOW SLUDGE tendency makes SPDA ideal for greases operating above 150°C where other aminics form deposits. Treat rate: 0.3-0.8%.

AntioxidantsBase Fluid Additives

Phenolic Antioxidant PH-115

Treat Rate: 0.1–0.5%

Sulfur-containing phenolic antioxidant for lubricant base oils and synthetic formulations.

AntioxidantsBase Fluid Additives

Phenolic Antioxidant BHT

Treat Rate: 0.1–0.5% in grease

Cost-effective antioxidant for general-purpose greases. Most economical antioxidant option. FDA approved for food contact. Best for moderate-temperature greases (<120°C). Note: H400/H410 aquatic toxicity.

AntioxidantsBase Fluid Additives

Phenolic Antioxidant PH-15S

Treat Rate: 0.3–0.5% in grease

Sulfur-phenolic antioxidant specifically for PAG-based greases. Dual functionality (primary + secondary antioxidant) makes this the BEST antioxidant choice for PAG base oil greases. Treat rate: 0.3-0.5%.

AntioxidantsBase Fluid Additives

Phenolic Antioxidant PH-135

Treat Rate: 0.3–0.5% in grease (synergistic with aminic)

Phenolic antioxidant for grease (synergistic with aminic). Classic turbine grease antioxidant system: 0.3% PH-135 + 0.5% AO-148. Non-staining, non-discolouring. Food-grade pathway via NSF HX-1.

AntioxidantsBase Fluid Additives

Aminic Antioxidant 5057

Treat Rate: 0.2–1.0%

Butyl Octyl Diphenylamine (BODPA). Alkylated diphenylamine antioxidant for turbine, hydraulic, and compressor oils. Liquid, easy handling. REACH registered.

AntioxidantsBase Fluid Additives

Aminic Antioxidant AO-148

Treat Rate: 0.3–0.8% in grease

Primary antioxidant for lithium, lithium complex, calcium, and polyurea greases. Most widely used aminic antioxidant in grease formulations. Treat rate: 0.3-0.8%. Synergistic with PH-135 for long-life greases. NSF HX-1 available via NA-LUBE AO-142 registration.

PAGs

PAG Hydraulic Thickener 18K

Pour Point: N/A°C

High-MW PAG thickener for water-glycol fire-resistant hydraulic fluids. ~18,000 mm2/s.

PAGs

PAG WS-320 Hydraulic Gear

Visc @40°C: 320 cStVI: 240Pour Point: -36°C

Water-soluble PAG, ISO VG 320. For synthetic hydraulic fluids and heavy gear applications. Fire-resistant.

PAGs

PAG WS-68 Compressor Metalworking

Visc @40°C: 68 cStVI: 200Pour Point: -40°C

Water-soluble PAG, ISO VG 68. Dual-purpose for compressor oils and metalworking fluids. High VI and thermal stability.

PAGs

PAG WS-20 Light Metalworking

Visc @40°C: 20 cStVI: 192Pour Point: -45°C

Water-soluble PAG, ISO VG 20. For light-duty metalworking fluids and grinding applications. Low foaming.

PAGs

PAG 56 Compressor Grade

Visc @40°C: 56 cStVI: 180Pour Point: -40°C

Water-insoluble PAG, ISO VG 56. Mid-range compressor grade bridging VG 46 and VG 68. Good all-round performance.

PAGs

PAG 32 Compressor Base

Visc @40°C: 32 cStVI: 160Pour Point: -46°C

Low-viscosity PAG base oil, ISO VG 32. For light-duty compressors and refrigeration systems. Excellent low-temperature flow.

PAGs

PAG 68 Compressor Grade

Visc @40°C: 68 cStVI: 180Pour Point: -45°C

Water-insoluble PAG base oil, ISO VG 68. For heavy-duty compressor and hydraulic applications. Excellent thermal stability and seal compatibility.

PAGs

PAG 46 Compressor Grade

Visc @40°C: 46 cStVI: 180Pour Point: -40°C

Water-insoluble polyalkylene glycol base oil, ISO VG 46. Engineered for rotary screw and reciprocating compressors. High VI, low pour point, non-carbon-forming.

Performance Comparison

PAG vs Mineral Oil vs PAO

How PAG base oils compare to mineral oil and PAO across key performance properties.

Property	PAG	Mineral Oil	PAO
Oxidation Stability	Excellent	Moderate	Good
Viscosity Index	> 200	95–110	130–140
Pour Point	≤ −40°C	−15 to −10°C	−40°C
Thermal Stability	Up to 260°C	Up to 150°C	Up to 180°C
Biodegradability	Readily biodegradable	Poor	Moderate
Seal Compatibility	FKM, HNBR, PTFE	Most seals (not silicone)	Most seals

Formulation Guidance

Compatible Additives

Antioxidant

DODPA (Octylated Diphenylamine)

0.5–1.0% for high-temperature hydraulic systems

Antifoam

Silicone-based antifoam

5–10 ppm to suppress foam in high-speed pump recirculation

Corrosion Inhibitor

Amine-based

Required for water-glycol formulations to protect ferrous components

Technical Reference

Technical Notes

Operating temperature range: −40°C to 200°C (anhydrous PAG); −20°C to 60°C (water-glycol HFC). Fire-resistant HFC formulations contain 35–45% water and require regular water content monitoring. Compatible with FKM and HNBR seals. Relevant standards: ISO 12922 (Fire-resistant hydraulic fluids, HFC category), DIN 51524 (Hydraulic oils), ISO 6743-4 (Hydraulic fluid categories).

Free Tools

Free Tools for This Application

Use our free online tools to find the right PAG grade, check compatibility, and calculate specifications for your application, no signup required.

PAG Technical Guide

Comprehensive PAG selection and properties reference, covering chemistry, viscosity, compatibility, and sourcing.

Viscosity Calculator

Calculate PAG viscosity at different operating temperatures using ASTM D341 regression.

All tools are free, no signup, no email required. Visit meecarigno.co.uk/resources to see all tools.

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