What Is Viscosity?

Viscosity is the measure of a fluid’s resistance to flow. In transformer oil, kinematic viscosity is typically measured in centistokes (cSt) at standard temperatures—commonly 40°C and 100°C. Viscosity affects how easily the oil circulates through the transformer’s cooling and insulating system.

Test Standard

ASTM D445 – Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and the Calculation of Dynamic Viscosity)

Key Gases Measured

Insulating Liquids – Measurement of Relative Permittivity, Dissipation Factor (Tan δ) and DC Resistivity.

DBPC Interpretation
Typical Acceptance Criteria
Temperature Ideal Range for New Mineral Oil Action if Out of Range
40°C 8 – 12 cSt Check for contamination or aging
100°C 2 – 4 cSt Evaluate oxidation or sludge
Why Viscosity Testing Is Important

Our Testing Process

  • Vacuum-sealed sample collection with barcode tracking
  • Automated kinematic viscosity measurement at controlled temperatures (40°C / 100°C)
  • Calibration using certified viscosity reference standards
  • Data logged into our ERP for tracking and reporting
  • AI-generated insights and recommendations included in report
Report Includes

Why Choose Tru-FIL?

  • ASTM D445-compliant lab procedures
  • NABL-grade calibrated viscometers and bath systems
  • ERP-integrated testing with historical trend tracking
  • Sample pickup from anywhere in India using vacuum-sealed bottles
  • 24/7 laboratory operations and rapid reporting