The sources give you the adjustment framework. Interval read from SKF's 70 °C base diagram and shortened when speed reaches 70–80 % of the applicable limit, when housing temperature exceeds about 60 °C, or under contamination. Plus fill rules of roughly one-third of free space at medium speed and 10–15 % at high speed.
Replenishment grams come from SKF's Gp = 0.005·D·B (side-fed) or 0.002·D·B (ring-groove-fed) for electric-motor bearings. No source publishes the actual interval hours, a contamination interval multiplier, or a numeric grease temperature limit, so you derive the interval from the manufacturer's diagram and verify the rest before ordering.
Is Your Operating Point Inside the Range Where a Standard Interval Applies?
Start by locating your operating speed against the applicable limit, because the interval framework only applies inside that range. SKF's relubrication-interval diagram is built on a base of 70 °C with a lithium-thickener, mineral-oil grease.
Any deviation from those conditions means adjusting the interval the diagram gives9. If the speed factor A exceeds 70 % of the recommended limit in SKF's table 4, or ambient temperatures are high, SKF recommends checking the operating temperature and grease suitability before trusting the base interval9.
Independent guidance converges on the same warning band: any operating speed within 80 % of the limiting speed should be scrutinised further. JTEKT asks customers to consult the manufacturer above 80 % of the catalog speed6,8.
The limit itself is not one number. SKF's speed-factor limits derate with load: for deep groove ball bearings the limit falls from 500,000 mm/min at C/P ≥ 15 to 300,000 mm/min at C/P ≈ 4, and roller types sit lower still9.
JTEKT's catalog limits likewise apply only at roughly C/P ≥ 16 and Fa/Fr ≤ 0.25 for standard designs8. You should check your load ratio before you check your speed.
If your point sits below the 70–80 % band and near the base conditions, the standard framework applies. If not, plan on a shortened interval or a conversation with the bearing manufacturer's application engineering service — SKF notes that high-performance greases may allow longer intervals, but only on request9.
How Contamination and Housing Temperature Should Shorten the Interval
Once you have a base interval in hand, two conditions pull it down, and the sources quantify them very differently. Temperature is the stronger lever.
Most users prefer to keep housings below 60 °C (140 °F); above that, grease lubrication requires specialised grease and much shorter re-greasing intervals6. For the underlying rate, one lubricant-lifecycle framework applies the Arrhenius rule, in which lubricant degradation rate doubles for each 10 °C rise in temperature1.
This is an oil-degradation rule from a general lubricant-life framework, not a grease-specific interval multiplier. Contamination is quantified in the life calculation but not converted into interval hours.
The JIS B 1518:2013 contamination factor e_c runs from 1 under laboratory-level cleanliness down to 0 under extremely high contamination, split by pitch diameter below and above 100 mm. It reduces the modified rating life21.
No source provides a multiplier that turns an e_c value, or a dirty-vs-clean environment, directly into a shorter relubrication interval; contamination enters the interval only qualitatively1,21.
You should treat heavy contamination and housing temperatures above 60 °C as reasons to shorten the interval and to ask the grease or bearing manufacturer for a specific derated figure rather than guessing one.
How Much Grease: Initial Fill Fraction and Replenishment Grams
Two separate decisions sit here: how much grease the cavity holds at assembly, and how many grams you add at each relubrication. The fill fraction follows speed; the replenishment grams follow bearing size and grease feed path.
For replenishment of electric-motor bearings, use the motor manufacturer's recommendation where one exists; otherwise the D·B formulas below apply16. Check which feed path your bearing uses before you calculate the dose, because the two formulas give different grams for the same bearing size.
| Fill type (initial vs replenishment) | Rule and unit | Valid condition |
|---|---|---|
| Initial fill, low speed | Cavity can be packed full | Churning losses almost negligible |
| Initial fill, medium speed | About 1/3 of free space | Good approximation at medium speeds |
| Initial fill, high speed | 10–15% of free space | High speed; excess grease resists motion and heats the bearing |
| Replenishment, side-fed | Gp = 0.005·D·B grams (D = OD mm, B = width mm) | Electric-motor bearings such as deep groove ball or cylindrical roller |
| Replenishment, ring-groove-fed | Gp = 0.002·D·B grams | Through annular groove and holes in the outer ring, e.g. spherical roller bearings |
Why More Grease Is Not Safer — Dosing a Hot Bearing
The fill rules exist because excess grease churns. Overfilling the bearing cavity raises operating temperature and can end in bearing failure.
Housings must therefore leave space for grease to be ejected during start-up, and high-speed motors should carry only a low grease level7. One supplier's guidance makes the same point for hot service: excess grease churns, generates more heat, oxidises quickly and can leak past seals13.
This changes how you respond to a hot bearing. Adding a full charge treats the symptom in the wrong direction — if anything, a hot bearing calls for more frequent but smaller grease doses, a rule one source states for high-temperature operation13.
You should measure the housing temperature with an infrared thermometer or thermocouple rather than estimating it, so you know whether you are chasing under- or over-lubrication13. If the housing runs above 60 °C, shorten the interval and reduce the dose per shot rather than increasing the charge6,13.
Warning Signs That Lubrication Is Overdue
Between scheduled intervals, these are the field signals the sources name for lubrication trouble or bearing distress. Note that rising temperature alone is ambiguous: it is both a symptom of depleted lubricant and the primary symptom of over-greasing.
You should pair it with the other checks before acting7,13.
- ✓Increased operating temperature, measured at the housing with an IR thermometer or thermocouple
- ✓Abnormal vibration; vibration analysis and thermography can predict failure before downtime
- ✓Unusual noise — grinding or clicking
- ✓Grease leaking past seals, a sign of over-lubrication in hot service
- ✓Visible raceway spalling found after disassembly — by then the damage is done, so treat the earlier signals as the action triggers
What to Demand From the Manufacturer and Grease Datasheet Before Finalising the Interval
Because no source in this set publishes actual interval hours, moisture multipliers or grease qualification data, the interval you write on the maintenance plan is only as good as the manufacturer documents behind it. Convert the gaps into explicit asks before you finalise the schedule.
- ✓Request the relubrication-interval diagram or calculation tool for your specific bearing and grease — the framework is public, the hour values are not
- ✓If speed exceeds 80% of the catalog or limiting speed, consult the bearing manufacturer before setting any interval
- ✓Ask how your C/P and Fa/Fr ratios modify the speed limit; catalog values carry load conditions such as C/P ≥ 16 and Fa/Fr ≤ 0.25
- ✓Ask the grease supplier for a numeric maximum temperature limit for the specific grease; the sources define such limits conceptually but give no per-grease number
- ✓Ask for an interval adjustment for contamination and moisture exposure; no published multiplier exists in this evidence set, so any figure must come from the manufacturer
- ✓Request grease qualification data (for example against DIN 51825 or ASTM D217) if your specification requires it; no such data appears in these sources
When Sources Disagree on the Quantity Rule: Which Figure to Trust
Not every published grease-quantity formula carries equal weight. One rule is backed by a bearing manufacturer's catalog; the other is a supplier's rule of thumb with an unvalidated 'bearing factor'.
Seeing the conflict side by side protects you from building a maintenance plan on the weaker figure.
| Grease quantity rule (grams / % free space) | One source reports | Another reports | What the buyer should do |
|---|---|---|---|
| Replenishment quantity (g) | Gp = 0.005·D·B or 0.002·D·B g, by feed path | (OD + width)/2 × bearing factor grams | Use the SKF D·B formulas; they are the manufacturer-backed ones |
| Applicability of 1/3 free-space fill | Good general rule for optimal performance | Valid only at medium speeds; high speed needs 10–15% | Match the fill fraction to your speed, not to habit |
| Sealed bearings | Manufacturers often pre-fill the correct amount | Small ball bearings usually greased-for-life, exceeding motor life | Check whether your bearing is capped before scheduling relubrication at all |
Before you request a quote
- The evidence leaves this open — put it to the supplier: no source reproduces actual relubrication-interval values in hours or the full SKF diagram; only the adjustment framework is published, so request the manufacturer's diagram or tool for your bearing and grease.
- The evidence leaves this open — put it to the supplier: no quantitative interval multipliers for contamination or moisture/water exposure exist in these sources; ask the bearing or grease manufacturer for a derated interval in your environment.
- The evidence leaves this open — put it to the supplier: whether to re-grease while running or stopped, and relief-valve practice, are not addressed by any source — confirm with the bearing manufacturer.
- Request a written quote with price basis, MOQ, tooling, payment terms and production lead time.
- The evidence leaves this open — put it to the supplier: no qualification test data against DIN 51825, ASTM D217 or IP 186 is available here; the standards cited are limited to ISO 281:2007 / JIS B 1518:2013 life calculation — request certification data if your spec requires it.
- The evidence leaves this open — put it to the supplier: no numeric maximum temperature limit (HTL) for any specific grease is given; limits are defined conceptually only — obtain the value from the grease datasheet.
- The evidence leaves this open — put it to the supplier: grease discoloration and increased motor current are not stated by any source as warning signs; do not rely on them without manufacturer backing.
Sources · 9
- 1machinerylubrication.comIndustry publication
- 2machinerylubrication.comIndustry publication
- 6amroll.comManufacturer technical documentation
- 7cdn.skfmediahub.skf.comManufacturer technical documentation
- 8koyo.jtekt.co.jpManufacturer technical documentation
- 10pibsales.comIndustry peer technical page2026-04
- 11duhui-bearing.comIndustry peer technical page2026-05
- 13duhui-bearing.comIndustry peer technical page2026-04
- 21koyo.jtekt.co.jpManufacturer technical documentation
Technical references cited for verifiability — not supplier recommendations.Browse the research library.