A fluid gear pump gear arranged to rotate about a first axis includes a concentrically disposed first hub portion and a plurality of first teeth radially projecting and circumferentially spaced about the first hub portion, the first hub portion and the first teeth being formed of a ceramic material. The gear also includes a first shaft on which the first hub portion is carried.

A fluid gear pump gear arranged to rotate about a first axis includes a concentrically disposed first hub portion and a plurality of first teeth radially projecting and circumferentially spaced about the first hub portion, the first hub portion and the first teeth being formed of a ceramic material. The gear also includes a first shaft on which the first hub portion is carried.

An internal combustion engine includes a combustion chamber, a fuel injector injecting fuel into the combustion chamber, a cylinder, a piston having a crown and reciprocating in the cylinder, the crown being exposed to the combustion chamber, and an ignition delay enhancer prolonging an ignition delay of a fuel-air mixture in the combustion chamber. A ceramic member is disposed on at least a fuel injection port, to which fuel is injected from the fuel injector, of the crown of the piston.

In a spark ignition engine, a thermal insulation thin layer is formed over a wall surface, facing an inside of a combustion chamber, of a base material forming the combustion chamber, and for a thermal conductivity [W/(m.Math.K)], a thermal diffusivity [mm.sup.2/s], and a thickness L [m] of the thermal insulation thin layer, L16.7 and L207.4().sup.0.5 are satisfied. With such a configuration, a heat loss Q_total escaping from gas in a cylinder to the wall of the combustion chamber over all strokes can be reduced, and the thermal efficiency can be improved without inducing degradation of knocking due to an increase in an amount of heating Q_intake of the gas in the cylinder during an intake stroke.