| Property | FC-40 | XP‑68 |
|---|---|---|
| Boiling Point | 165 °C; operating range –57 °C to 165 °C | 165 °C (identical by spec) |
| Pour/Freezing Point | –57 °C | –57 °C |
| Density | 1855 kg/m³ | Similar |
| Kinematic Viscosity (25 °C) | 2.2 cSt (abs: 4.1 cP) | Similar |
| Dielectric Constant | 1.9 @ 1 kHz | 1.8–2.0 |
| Dielectric Strength | 46 kV (0.1" gap) | ≥40 kV |
| Thermal Conductivity (25 °C) | 0.065 W/m·K | Approx same |
| Latent Heat of Vaporization | 69 J/g | Approx same |
| Surface Tension | 16 dynes/cm | — |
| Water Solubility | <5 ppmw | — |
| GWP / ODP | Zero ODP; high GWP | Same |
| Materials Compatibility | Excellent with most metals/plastics | Same |
| Toxicity & Safety | Low toxicity, nonflammable | Low toxicity |
