CRE's Choice: The choice of a ceramic is complicated by particular attributes that are present in some ceramics and not in others. Furthermore, our choice of ceramic is made more difficult by the dearth of uses, short history and only a small dataset of ceramic applications. In contrast, metals and alloys have an extensive and long history of activity and a considerable amount of data to rely upon. On careful consideration we have decided on a ceria-based zirconia engineering ceramic for the following reasons: (1) its relatively good mechanical strength (i.e. combination of high fracture toughness and high bend strength); (2) the twin properties of the zirconias that are clearly useful to heat engines; (3) tests which show that CeTZP zirconia ceramic does not suffer from hydrothermal degradation which plagues several other ceramics; (4) being an oxide, zirconia is unlikely to be further oxidized. Considering that many fuels contain chemically-active and corrosive substances, resistance against hydrothermal degradation and resistance against oxidation are highly desirable attributes of a ceramic for an internal combustion engine.