See why an aircraft grease cross-reference chart is only a screening tool, and how to verify specification, compatibility and approval.
No. An aircraft grease cross-reference chart can identify a possible equivalent, but it does not by itself make that lubricant approved. Approval must come from the applicable aircraft or component maintenance data, the specified material standard, an authorised substitution, and the maintenance organisation’s controlled procedures for that exact lubrication point.
In real-world aviation maintenance, we treat a cross-reference as a screening tool. It can shorten the search for a replacement grease, but every candidate still needs to be checked against the controlling technical data.
What does a grease cross-reference chart actually prove?
Usually, it proves only that the chart’s publisher considers two products broadly comparable. That comparison may be based on viscosity, thickener type, temperature range or an industry specification, but it does not necessarily cover qualification status, additives, material compatibility or the aircraft manufacturer’s approval.
| Chart wording | What it normally means | Is it enough? |
|---|---|---|
| Equivalent or alternative | A candidate with broadly similar characteristics | No; verify it against the controlling maintenance data |
| Meets or conforms to a specification | The supplier claims compliance with the named specification | Only if the data accepts that specification and does not require separate qualification or listing |
| Qualified or approved product | The exact product may appear on a required approved-products list | Verify the product, grade, specification revision and listing status |
| Superseded by | A newer product may formally replace the old one | Accept only when the supersession comes from an authority recognised by the maintenance data |
A grease approved for one bearing, hinge or actuator is not automatically approved elsewhere on the same aircraft. Loads, operating temperatures, seals, bushes, corrosion protection and exposure to water can differ substantially.
How do you verify an approved aircraft grease?
Verify the lubricant from the most specific and authoritative maintenance instruction that applies to the aircraft, component and lubrication point.
- Identify the controlling document. Start with the aircraft maintenance manual, component maintenance manual, lubrication chart, service instruction or other approved data. For owner-permitted servicing, the aircraft-specific handbook may also contain binding limitations; our explanation of how a Cessna POH controls aircraft operation and servicing shows why generic advice cannot override model-specific documentation.
- Read the requirement exactly. Determine whether it specifies a particular product, a material specification, a grade, an approved-products list or an internal lubricant code. Check the document revision and any temperature or application restrictions.
- Establish the substitution authority. A supplier’s chart is not equivalent to a manufacturer’s supersession notice. If the prescribed product is unavailable, use a substitution expressly permitted by the controlling data or obtain an authorised engineering disposition.
- Confirm qualification and traceability. Check the exact product designation, specification revision, batch documentation, shelf life and packaging condition. A similar brand name or newer formulation may represent a different product.
- Check compatibility with the existing grease. Confirm base oil, thickener and additive compatibility, along with suitability for seals and adjacent materials. Follow any cleaning, purging or relubrication procedure stated in the maintenance data.
- Record the work correctly. Document the lubricant and the authority used for the substitution under the applicable maintenance system. Our summary of controlled maintenance data and traceability requirements explains why an undocumented cross-reference is not an adequate release basis.
Common grease-selection mistakes
The most frequent error is matching grease by appearance or a few headline properties rather than its complete approval basis.
- Choosing by colour: grease colour is not a reliable indication of chemistry, performance or compatibility.
- Using an automotive substitute: a general-purpose grease may lack the temperature performance, corrosion protection or material compatibility required in an aircraft application.
- Ignoring the specification revision: matching an old or similarly named standard may not satisfy the requirement in the applicable maintenance data.
- Assuming one grease fits the whole aircraft: wheel bearings, airframe hinges, flight-control components and specialised mechanisms may require different products.
- Contaminating the product: an unlabelled or shared grease gun can introduce an incompatible lubricant even when the correct cartridge was selected.
Can different aircraft greases be mixed?
Different aircraft greases should not be mixed unless compatibility is established and the maintenance procedure permits it. Incompatible thickeners or additives can cause softening, hardening, oil separation, loss of corrosion protection or poor lubrication under load.
A table describing two products as equivalents does not prove that they can be mixed in service. When changing grease, the instructions may require removal of the old material, cleaning, purging with the replacement and a shortened initial inspection or relubrication interval.
What if the specified aircraft grease is obsolete?
An obsolete grease must be replaced through a documented supersession or authorised substitution, not by choosing the nearest product on a commercial chart. Check revised aircraft and component data first, because a formal replacement may already be specified.
If no replacement is published, the appropriate manufacturer, design authority or authorised engineering function must assess the proposed product. The assessment should address specification compliance, qualification status, operating limits, compatibility and any transition procedure. Until that approval exists, the cross-reference chart supplies a candidate—not an approved lubricant.