Salpn is the common name for a chelating ligand, properly called N,N′-bis(salicylidene)-1,2-propanediamine, used as a motor oil additive.

The abbreviation "salpn" is also sometimes used for the structural isomer N,N′-bis(salicylidene)-1,3-diamino­propane and its conjugate base,[2] derived from 1,3-diaminopropane rather than 1,2-diaminopropane.

Trace metals degrade the fuels by catalyzing oxidation processes that lead to gums and solids.

Copper has the highest catalytic activity in fuel, and salpn forms a highly stable square planar complex with the metal.

[3] Salpn is preferred over salen, possibly because it has higher solubility in non-polar liquids.