Castrol Optigear Synthetic 800/320
ISO VG 320 extreme pressure gear oil
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Key specs
| Spec | Value | Method |
|---|---|---|
| KV40 | 320 cSt | ASTM D445 |
| KV100 | 50 cSt | ASTM D445 |
| Viscosity index | 230 | ASTM D2270 |
| Pour point | -30 °C | ASTM D97 |
| Flash point | 290 °C | ASTM D92 |
| Density at 15 °C | 1.074 g/cm³ | typical |
Grade checks
- KV40 is inside ISO VG 320 (288–352 cSt).
- Computed viscosity index is 220 from the stored KV40 and KV100 (ASTM D2270). The listed index is 230, more than 2 points away.
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: V PAG
- AGMA class: AS
- FZG fail stage: >=12
- Copper: 1A
- Note: For the lubrication of heavily loaded gears, brushings and bearings over a wide temp
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 |
|---|---|---|
| Shell Omala S4 WE 320 | 80 | same ISO 320, VI 230 vs 230, additive ep, synthetic, AGMA AS |
| Shell Omala S3 A 320 | 15 | same ISO 320, VI 200 vs 230, synthetic |
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 2026-09-09.
Related: Castrol, Optigear Synthetic 800, viscosity index calculator, ISO / SAE / AGMA chart.
Questions
Is Castrol Optigear Synthetic 800/320 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 800/320 equivalent?
Published oils in the same application and grade include Shell Omala S4 WE 320. 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 800/320 be mixed with mineral oil or PAO?
No. This oil is a PAG (polyalkylene glycol). PAG does not mix with mineral oil or PAO. Drain and flush before changing into it or out of it.
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