Disclosed are journal bearing assemblies, methods for making and methods for using journal bearing assemblies, and motor vehicles employing journal bearing assemblies. A disclosed friction-reducing journal bearing assembly includes a first (upper) bearing shell insert and a second (lower) bearing shell insert. Each insert mounts inside a bore, e.g., of an engine block or piston connecting rod, and has an arcuate inner-diameter (ID) surface. These ID surfaces are adjoined at opposing ends thereof to cooperatively define a cylindrical channel that receives therethrough a journal portion of a shaft (e.g., crankshaft or crank pin). The inner-diameter and/or outer-diameter (OD) surface of the second insert includes one or more axially elongated and/or one or more axially angled grooves, each of which extends only partially across the axial width of the shell insert. The lower insert may be fabricated with two axially elongated grooves extending generally orthogonally from respective edges of the insert.