Overview
Polymethacrylate (PMA) viscosity index improvers are coil-polymer additives that reduce the rate of viscosity change with temperature, enabling multi-grade lubricants to perform across wide temperature ranges. At low temperatures, the coiled polymer occupies minimal volume; at high temperatures, it expands and increases the effective viscosity of the base oil, raising the VI. PMA is particularly valued for its excellent low-temperature performance (MRV and Brookfield viscosity) compared to OCP-type VII, making it the preferred choice for hydraulic fluids, automotive gear oils, ATF, and arctic-grade lubricants. Shear stability (PSSI or SSI) is a critical selection parameter. High-shear-stability grades are required for automotive gear oils and ATF, while lower PSSI grades are used where thickening efficiency is paramount.
Hydraulic Oil Grades
| Chemistry | KV @100°C (mm²/s) | PSSI / SSI |
|---|
| PMA Viscosity Index Improver (Hydraulic, Standard) | 1100–1850 | SSI: 38 (KRL 20h) |
| PMA Viscosity Index Improver (Hydraulic) | 698 | PSSI: 38 (KRL 20h) |
| PMA Viscosity Index Improver (Hydraulic) | 800 | SSI: 38 (KRL 20h) |
| PMA Viscosity Index Improver (Hydraulic, High VI) | 1450 | PSSI: 65 (KRL 20h) |
Arctic / Cold Climate Grades
| Chemistry | KV @100°C (mm²/s) | PSSI / SSI |
|---|
| PMA Viscosity Index Improver (Arctic) | 1500 | PSSI: 25 (KRL 20h) |
| PMA Viscosity Index Improver (Arctic) | 1300 | PSSI: 35 (KRL 20h) |
| PMA Viscosity Index Improver (Arctic, Very Cold) | 850 | PSSI: 50 (KRL 20h) |
| PMA Viscosity Index Improver (Arctic, Very Cold) | 770 | PSSI: 65 (KRL 20h) |
Automotive Gear Oil Grades
| Chemistry | KV @100°C (mm²/s) | PSSI / SSI |
|---|
| PMA Viscosity Index Improver (Gear Oil, High Shear Stability) | 460 | SSI: 22 (KRL 20h) |
| PMA Viscosity Index Improver (Gear Oil) | 700 | SSI: 29 (KRL 20h) |
| PMA Viscosity Index Improver (Gear Oil, Cost-effective) | 775 | PSSI: 40 (KRL 20h) |
ATF / Driveline Grades
| Chemistry | KV @100°C (mm²/s) | PSSI / SSI |
|---|
| PMA Viscosity Index Improver (ATF) | 575 | PSSI: 10 (KRL 20h) |
| PMA Viscosity Index Improver (ATF, Dispersant Type) | 700 | PSSI: 35 (KRL 20h) |
| PMA Viscosity Index Improver (ATF, High Shear Stability) | 700 | PSSI: 42 (KRL 20h) |
| PMA Viscosity Index Improver (Multi-grade Engine Oil) | 1250 | PSSI: 12 (Bosch 30 cycles) |
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