Hydraulic Fluids
Background & Properties
castrol.com/GPS
800 255 4417
May 2025
GPS
Industry Specifications
Test Criteria P-68, P-69 HF-O
and P-70
Viscosity change, (%), max 5
Neutralization number, (%), max ±50
Sludge (mg/100 ml), max 25 100
Copper wt loss (mg), max 10
Copper rod appearance 5 Report
Iron rod appearance No discoloration
1000-h Sludge (ASTM D 4310)
is test measures the build-up of sludge and increase of iron and copper particulate in the oil.
Test Criteria Denison HF-O HF-1 HF-2
TAN (mg KOH), max 1.0 .2 1.0
Insoluble Sludge, mg max 100 100 400
Total Cooper, mg max 200 - 200
Total Iron, mg max 50 - 100
TAN (ASTM D 974-07)
Standard Test Method for Acid and Base Number by Color-Indicator Titration
Importance of Wear and Load Tests
Load performance and wear protection are crucial components when selecting a hydraulic fluid. Hydraulic
fluids are designed to handle important shock loads and other various types of loads during operation. e
ability to prevent metal to metal contact also results in lowering component wear, such as in hydraulic pumps.
Proper viscosities and excellent anti-wear additives play a pivotal in protecting against wear.
Types of Wear and Load Tests include:
Vickers 35VQ-25 Vane Pump Test
is test measures wear to the cam ring and the vane pump. It is run for three, 50-hour segments at 200°F,
3,000 psi and 2400 rpm.
Test Criteria
Ring 75-mg max
Vane 15 mg max
Total 90 mg max
C3
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