Crankshaft and main bearing assembly for a reciprocating piston internal combustion engine, the assembly including: a crankshaft having a first main bearing journal, a second main bearing journal axially aligned with and spaced from and positioned between the first main bearing journal, and at least a first crankpin journal parallel with, but radially spaced from the first and second main bearing journals (10, 20), the at least first crankpin journal being interposed between a first radially extending crank arm associated with the first main bearing journal and a second radially extending crank arm associated with the second main bearing journal; a first main bearing sleeve receiving the first main bearing journal, the first bearing sleeve having a circumferential groove in an inner bearing surface thereof to supply fluid lubricant to the first bearing journal; and a second main bearing sleeve receiving the second main bearing journal, the second bearing sleeve having a circumferential groove in an inner bearing surface thereof to supply fluid lubricant to the second bearing journal, wherein the first main bearing journal defines an outer circumferential surface with a first primary entrance opening therein for receiving fluid lubricant from the circumferential groove of the first main bearing sleeve,wherein the second main bearing journal defines an outer circumferential surface with a second primary entrance opening therein for receiving fluid lubricant from the circumferential groove of the second main bearing sleeve, wherein the at least first crankpin journal defines on outer circumferential surface with a single exit opening therein to supply fluid lubricant to the at least first crankpin journal, wherein at least one of the first and second primary entrance openings (11, 21) is in fluid communication with the single exit opening of the at least first crankpin journal, wherein the first main bearing journal on its outer circumferential surface has a first secondary entrance opening circumferentially spaced from the first primary entrance opening to be substantially radially opposite thereto for also receiving fluid lubricant from the circumferential groove, wherein the second main bearing journal on its outer circumferential surface has a second secondary entrance opening circumferentially spaced from the second primary entrance opening to be substantially radially opposite thereto for also receiving fluid lubricant from the circumferential groove, wherein the second primary entrance opening of the second main bearing journal is in an angularly spaced position with respect to the first primary entrance opening of the first main bearing journal, which angularly spaced position is oriented at an angle substantially greater than 0 degrees, but substantially less than 180 degrees from the first primary entrance opening, wherein the first secondary and second secondary entrance openings (12, 22) are in fluid communication with the single exit opening of the at least first crankpin journal, and wherein the circumferential grooves (277, 279) of the first and second main bearing sleeves (210, 220) each extend over substantially less than 180 degrees of the respective inner bearing surface.