Castrol Optigear Synthetic X/320
ISO VG 320 gear oil
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Key specs
| Spec | Value | Method |
|---|---|---|
| KV40 | 325 cSt | ASTM D445 |
| KV100 | 40.8 cSt | ASTM D445 |
| Viscosity index | 179 | ASTM D2270 |
| Pour point | -45 °C | ASTM D97 |
| Flash point | 250 °C | ASTM D92 |
| Density at 15 °C | 0.852 g/cm³ | typical |
Grade checks
- KV40 is inside ISO VG 320 (288–352 cSt).
- Computed viscosity index is 180, within 2 points of the listed 179.
Viscosity and temperature
ASTM D341 (Walther) fitted to the published KV40 and KV100. It is an interpolation between those two points, and it is not meaningful below the pour point. Move the control to read a temperature.
Classification
- Category: Gear
- Synthetic: Unlisted
- Base oil: IV PAO
- AGMA class: AS
- FZG fail stage: >=14
- Copper: Unlisted
- Note: Premium synthetic oils for industrial gears operating at wide temperature fluctuations and high loads
Equivalents
| Oil | Score | Why |
|---|---|---|
| Mobil Mobil SHC Gear OH 320 | 54 | same ISO 320, VI 178 vs 179, pour -45 vs -45, AGMA AS, buyable now |
| Shell Omala S4 GXV 320 | 50 | same ISO 320, VI 169 vs 179, pour -42 vs -45, flash within 15 °C, AGMA AS, buyable now |
| Mobil Mobil SHC 632 | 48 | same ISO 320, VI 172 vs 179, pour -48 vs -45, AGMA AS, buyable now |
| Mobil Mobil SHC Gear 320 | 48 | same ISO 320, VI 181 vs 179, pour -48 vs -45, AGMA AS |
| Shell Omala S5 Wind 320 | 46 | same ISO 320, VI 170 vs 179, pour -48 vs -45, flash within 15 °C, AGMA AS |
Scores use published typical data. This is not an exact equivalent, and it is not an OEM approval. Confirm the substitute with the machine builder.
Documents
- Product data sheet
- Safety data sheet
- Specs last read from the data sheet on 2026-09-10.
Related: Castrol, Optigear Synthetic X, viscosity index calculator, ISO / SAE / AGMA chart.
Questions
Is Castrol Optigear Synthetic X/320 an ISO VG 320 oil?
Yes. The catalogue lists it as ISO VG 320, which is a kinematic viscosity of 320 cSt at 40 °C, plus or minus 10 percent (288 to 352 cSt). Confirm the current data sheet before you fill a machine.
What is a Castrol Optigear Synthetic X/320 equivalent?
No other brand in this catalogue clears the equivalents bar for this oil yet (same application, same grade, compatible base oil, and a score of 60 or more). That is not proof that nothing else works. Check the machine manual.
Can Castrol Optigear Synthetic X/320 be mixed with another oil?
Mixing two oils that share a base family is sometimes done and sometimes a mistake. Do not mix this oil with a PAG. For any other mix, follow the maker's change-over guidance and the machine manual.
Report a data error
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