The temperature a grease reaches, heated in a small test cup under ASTM D566 or D2265, when its first drop falls through the hole in the bottom. It marks where the thickener melts or loses its structure, so it rates heat resistance but is not an operating limit: greases usually run 50 to 100 C below it because the base oil oxidizes long before the thickener fails. Simple lithium drops near 190 C, while lithium complex, polyurea and calcium sulfonate typically drop above 240 C.
Dropping point's 280, but don't let that fool you, the base oil cooks off way before that.
Salespeople quote dropping point as if it were a maximum service temperature. Ask for the upper operating temperature on the data sheet instead.
Also heard as
- drop point
- DP
Related terms
Lithium complex
Grease thickener made from a lithium soap plus a complexing acid, the all-purpose bearing workhorse.
Thickener
Solid structure in a grease, usually a metal soap or polyurea, that holds the base oil like a sponge.
Grease
Semi-solid lubricant made of oil held in a thickener sponge, usually with additives.
Calcium sulfonate
Grease thickener based on overbased calcium sulfonate, known for water resistance and built-in EP protection.