Castrol Optigear RMO
ISO VG 150 extreme pressure gear oil
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Key specs
| Spec | Value | Method |
|---|---|---|
| KV40 | 150 cSt | ASTM D445 |
| KV100 | 18 cSt | ASTM D445 |
| Viscosity index | 133 | ASTM D2270 |
| Pour point | -48 °C | ASTM D97 |
| Flash point | 190 °C | ASTM D92 |
| Density at 15 °C | 0.879 g/cm³ | typical |
Grade checks
- KV40 is inside ISO VG 150 (135–165 cSt).
- Computed viscosity index is 133, within 2 points of the listed 133.
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
- Copper: Unlisted
- Note: Multi-grade, synthetic
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 629 | 55 | same ISO 150, VI 166 vs 133, additive ep, synthetic, pour -48 vs -48, buyable now |
| Mobil Mobil SHC Gear 150 | 55 | same ISO 150, VI 176 vs 133, additive ep, synthetic, pour -54 vs -48, buyable now |
| Chevron Meropa Synthetic EP 150 | 51 | same ISO 150, VI 162 vs 133, additive ep, synthetic, pour -51 vs -48 |
| Chevron Tegra Synthetic Gear 150 | 51 | same ISO 150, VI 162 vs 133, additive ep, synthetic, pour -49 vs -48 |
| Shell Omala S4 GXV 150 | 50 | same ISO 150, VI 169 vs 133, additive ep, synthetic, pour -45 vs -48 |
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 RMO, viscosity index calculator, ISO / SAE / AGMA chart.
Questions
Is Castrol Optigear RMO an ISO VG 150 oil?
Yes. The catalogue lists it as ISO VG 150, which is a kinematic viscosity of 150 cSt at 40 °C, plus or minus 10 percent (135 to 165 cSt). Confirm the current data sheet before you fill a machine.
What is a Castrol Optigear RMO 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 RMO 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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