By Lukeron Lubricants · Last updated
Quick answer
Use gear oil in enclosed gearboxes with an oil bath, splash or circulation system, and at higher speeds and loads. Use a soft grease (usually NLGI 000, 00 or 0) only where the machine maker names it, such as slow-speed, leaking, vertical or open gears. Do not mix the two or swap without the maker's approval. The manual decides.
Gear oil and grease in gearboxes compared
| Gear oil | Grease | |
|---|---|---|
| Form | Liquid, flows to the gears | Oil held in a thickener, stays in place |
| Carries heat away | Yes | Little |
| Leak risk | Higher with worn seals | Lower |
| Usual fit | Enclosed gearboxes, higher speed and load | Slow-speed, open or leaking gearboxes, when the maker names it |
| Typical grade | ISO VG, for example 220 or 320 | NLGI 000, 00 or 0 for gearboxes |
General guidance only. Follow the machine maker's manual for product, grade and fill level.
Most gearboxes run on gear oil. Some run on grease. The right choice depends on how the gearbox is built, how fast and how hot it runs, and whether the housing can hold oil. This guide explains the difference in plain words, when each one is the better choice, and what to check before you switch.
Gear oil or grease: the short difference
Gear oil is a liquid. It flows, splashes over the gears, carries heat away and carries wear particles to the sump or filter. Grease is oil held in a thickener. It stays where you put it, seals against dirt and does not leak easily, but it does not flow back to the gears once they have pushed it aside.
When gear oil is the better choice
- Enclosed gearboxes with an oil bath, splash lubrication or a circulation system.
- Higher speeds and higher loads, where heat must be carried away.
- Worm gears, which run with a lot of sliding and usually need the grade the maker names.
- Gearboxes with a sight glass, drain plug and fill plug, which are made for oil changes.
In these gearboxes, grease usually cannot move fast enough to keep reaching the contact, so the gears can run short of lubricant.
When grease is the better choice
- Slow-speed or lightly loaded gearboxes that the maker designs for semi-fluid grease.
- Gearboxes that leak oil because the seals are worn or the shaft is vertical.
- Open gears and exposed drives, where oil would be thrown off.
- Sealed-for-life units and gearboxes where the maker specifies grease.
In gearboxes, the grease is usually a soft one, NLGI 000, 00 or 0, so it can still flow back to the gears. A stiff grease such as NLGI 2 can leave a channel around the gears.
Why you should not simply swap one for the other
- A gearbox made for oil can run hot on grease, because grease does not carry heat away.
- A gearbox made for grease can leak or churn if you fill it with oil it was not designed for.
- Mixing oil and grease in one gearbox is a bad idea. Drain, clean and refill with the product the maker names.
Always follow the machine maker's manual first. It names the product type, the grade and the fill level.
How to choose in four steps
- Read the manual or nameplate. If it names gear oil with a grade such as ISO VG 220 or 320, use that.
- If the manual names grease, use the NLGI grade it names. For gearboxes this is often 00 or 0.
- If the manual does not say, look at the build: oil bath and sight glass means oil, sealed unit with a grease nipple means grease.
- If you are unsure, ask the maker or ask us with the machine name and model.
Quick summary
- Enclosed gearboxes with oil baths and circulation systems use gear oil.
- Slow-speed, leaking, vertical and open gears sometimes use a soft grease.
- Do not mix oil and grease, and do not swap without the maker's approval.
- The manual decides. When in doubt, ask.
Gear oils and greases from Lukeron
Lukeron makes industrial gear oils and greases at its own plant in Anandpar, Jamnagar, Gujarat, including EP gear oils in ISO VG 220, synthetic and worm gear oils, and greases in NLGI grades 0 to 3. Tell us the machine, the maker's recommendation and your operating conditions, and our team will suggest a product. Free samples are available for testing.