An internal combustion engine includes a piston assembly with a piston rotatably connected to a pin carrier. The piston can rotate about a cylinder axis from a low compression ratio orientation to a high compression ratio orientation when an electronically controlled pump of a compression ratio controlled fluid circuit is activated. The piston includes a plurality of first wedges in contact with a plurality of respective second wedges of the pin carrier in a hydraulic chamber. The first wedges have hydraulic surfaces exposed to fluid pressure in the hydraulic chamber in order to hydraulically rotate the piston relative to the pin carrier. The engine may be configured to burn diesel fuel and natural gas.