Castrol Optigear Synthetic A/100
ISO VG 100 extreme pressure gear oil
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Key specs
| Spec | Value | Method |
|---|---|---|
| KV40 | 98 cSt | ASTM D445 |
| KV100 | 13.8 cSt | ASTM D445 |
| Viscosity index | 140 | ASTM D2270 |
| Pour point | -45 °C | ASTM D97 |
| Flash point | 220 °C | ASTM D92 |
| Density at 15 °C | 0.855 g/cm³ | typical |
Grade checks
- KV40 is inside ISO VG 100 (90–110 cSt).
- Computed viscosity index is 142, within 2 points of the listed 140.
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
- Attribute: Extreme Pressure
- Synthetic: Synthetic
- Base oil: PAO
- Copper: 1A
- Note: Wear protection under extreme thermal loads and operating conditions
Sulfur, EP additives and yellow metal
Extreme-pressure gear oils use sulfur compounds so steel teeth do not weld under shock. That same sulfur can tarnish or pit copper, brass and bronze: a bronze worm wheel, a brass cage, a cooler tube. ASTM D130 sits a polished copper strip in the oil and scores the colour. 1A and 1B are the ratings to keep when yellow metal shares the oil. The strip below is that test at room temperature.
How lubricant-induced copper corrosion works
Equivalents
| Oil | Score | Why |
|---|---|---|
| Mobil Mobil SHC 627 | 63 | same ISO 100, VI 162 vs 140, additive ep, synthetic, pour -48 vs -45, flash within 15 °C |
| Mobil 600 XP 100 | 35 | same ISO 100, VI 97 vs 140, additive ep, flash within 15 °C, buyable now |
| Shell Omala S2 G 100 | 30 | same ISO 100, VI 100 vs 140, additive ep, buyable now |
| Shell Omala S2 GX 100 | 30 | same ISO 100, VI 99 vs 140, additive ep, flash within 15 °C |
| Chevron Meropa 100 | 25 | same ISO 100, VI 100 vs 140, additive ep |
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
Related: Castrol, Optigear Synthetic A, viscosity index calculator, ISO / SAE / AGMA chart.
Questions
Is Castrol Optigear Synthetic A/100 an ISO VG 100 oil?
Yes. The catalogue lists it as ISO VG 100, which is a kinematic viscosity of 100 cSt at 40 °C, plus or minus 10 percent (90 to 110 cSt). Confirm the current data sheet before you fill a machine.
What is a Castrol Optigear Synthetic A/100 equivalent?
Published oils in the same application and grade include Mobil Mobil SHC 627. The match is from typical data-sheet values, not from an OEM approval. It is not an exact equivalent. Confirm the substitute with the machine builder.
Can Castrol Optigear Synthetic A/100 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.
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