For a typical reciprocating internal combustion engine with a piston, cylinder, connecting rod and crankshaft, there will be unnecessarily high side thrust acting on the piston in high-speed motion during the power stroke. This inherent side thrust will induce extra rubbing friction force and wear on the cylinder wall, thus reducing the engine power output. As a solution to this, the piston rings/crown can be innovatively redesigned to produce a transverse gas pressure to counteract the piston side thrust due to the tilting connecting rod. Thus the piston will move in the cylinder in a gas-cushioned manner to reduce adverse mechanical effects. Naturally, due to various engine limitations, this technology of gas-cushioned piston can be designed to be most effective only under certain operating conditions, such as a specific economical cruise speed of a ship or aircraft. In conjunction, the associated dynamics analysis and design of engine reciprocating mechanism is greatly enhanced by employing an ingenious varied-mass lumping method combined with the percussion concept developed by the author.