Gearboxes in Indian plants run conveyors, mixers, crushers, kilns and cooling towers, often for years on whatever oil was in the store. Getting the viscosity right is one of the easiest ways to stop pitting, overheating and early bearing failures.
ISO VG 220 suits most general enclosed gearboxes. Move to VG 320 or 460 for slow, heavily loaded or hot-running gearboxes, and to VG 150 for faster, lightly loaded units or cold starts. Always follow the gearbox maker's recommendation first: it reflects the gear speed and load the box was designed for.
As with hydraulic oil, the ISO VG number is the viscosity in centistokes at 40 °C, ±10%. Gear oils use thicker grades because gear teeth slide and roll under very high contact pressure.
Gearbox makers combine these using the pitch-line speed of the slowest gear stage and the ambient temperature, which is why their recommendation should come first.
| Application | Usual grade | Notes |
|---|---|---|
| High-speed or lightly loaded gearboxes | VG 150 | Also for cold starts |
| General conveyors, mixers, agitators, fans | VG 220 | The most common grade |
| Heavily loaded or hot-running units, crushers, mills | VG 320 | Common upgrade in hot climates |
| Slow, heavy drives, many worm gearboxes | VG 460 | Check worm-gear compatibility |
| Very slow, very heavy or high-temperature drives | VG 680 | As specified by the maker |
Whether your gears need EP additives at all is a separate decision. We explain it in EP vs non-EP gear oil.
Moving up is not free: thicker oil adds churning losses and runs hotter in fast gearboxes. That is why "thicker is safer" is a myth; see why thicker oil is not always better.
PAO-based synthetic gear oils keep their viscosity better across temperatures, resist oxidation longer and can extend change intervals. They earn their price in hot, hard-to-reach or critical gearboxes. Check seal compatibility, and do not mix PAG-based oils with mineral or PAO oils.
Can I use gear oil 320 instead of 220?Often yes in hot-running or heavily loaded gearboxes, if the maker allows it. In fast gearboxes the thicker oil can raise temperature and losses, so check temperature after the change.
What is the difference between gear oil 220 and hydraulic oil?Gear oil is much thicker (VG 220 against VG 32–68) and usually carries EP additives for tooth contact. Hydraulic oil is designed for pumps and valves. They are not interchangeable.
Can I use automotive gear oil (80W-90) in an industrial gearbox?It is not ideal. Automotive GL-5 oils use different additive packages that can attack bronze parts and may foam in industrial boxes. Use an industrial gear oil of the right grade.
How often should industrial gear oil be changed?Many mineral gear oils run 5,000–10,000 hours, and synthetics longer, but condition matters more than hours. Oil analysis is the reliable way to decide.
Send us the gearbox make, ratio, motor speed and running temperature, and our team will recommend the gear oil grade and type.