Abstract: The present invention discloses a structural oil pan for use with an internal combustion engine having a crankcase with short side walls of the type that generally do not extend below the center line of the crankcase. The oil pan has internal ribs which slidingly receive lower portions of the main bearing caps. The main bearing caps are fixed, relative to the oil pan with bolts passing through openings in the pan to threadingly engage corresponding openings in the bearing caps. Such an oil pan design allow the crankcase side walls, the crankshaft main bearing caps and the oil pan side walls to be structurally joined to resist vibration and noise generation. Weight savings are recognized by the oil pan of the present invention as the need for an engine block having extended side walls and increased weight is supplanted by a light weight, structurally rigid oil pan.