Pipette tip couplers, pipette tips, coupler and tip combinations, and methods for coupling and decoupling a pipette tip to or from an expanding mandrel collet coupling device. The pipette tip couplers include a central body, a spacer with cogs circumscribing the central body, an expanding mandrel collet circumscribing the spacer having an annular base and circumferentially spaced apart upwardly extending collet arms, and an elastomeric element circumscribing the central body. The cogs protrude through spaces between the collet arms. The collet arms are attached to the annular base and configured to expand between a first and a second circumference for engaging a first interior surface of the tip, with the elastomeric element sealing against a second interior surface below the first surface, and with an abutment between the cogs and a stepped interior shoulder of the pipette tip disposed between the first and second interior surfaces.