Definition
A lubricating grease made by combining a petroleum or synthetic oil with a calcium (lime) soap as the thickener. It has good water resistance but a relatively low maximum operating temperature, typically breaking down above about 175°F (80°C), which limits its use in high-temperature aircraft applications.
Plain English
A type of grease that uses a calcium-based soap to hold the oil together. It handles water well but cannot take much heat before it breaks down.
Context Anchor
Seen in aircraft maintenance references when choosing grease for parts that may be exposed to moisture.
Derivation
The name comes from 'lime,' an old term for calcium oxide or calcium hydroxide. Calcium compounds were used to make the soap that thickens the oil, so the grease became known as lime grease.
Why Pilots Care
Maintains lubrication and prevents corrosion on critical moving parts that are routinely exposed to rain, dew, or de-icing fluids.
Intuition Check
Do not read lime as citrus or green color here. In lime grease, lime means a calcium-based ingredient used to help make the grease thick and water-resistant.
Example Sentence 1
The mechanic checked the lubrication chart and selected a high-temperature grease instead of lime grease for the wheel bearings.
Example Sentence 2
During preflight, the pilot checked that all accessible hinges had been recently serviced with lime grease.