Shared Power: How the Boeing 747-8 and 787 Dreamliner Utilize the Same GEnx Engine
It is true that both the Boeing 747-8 and the 787 Dreamliner can be powered by the General Electric GEnx engine. However, they use different variants tailored to their specific needs. The four-engine 747-8 uses the GEnx-2B, which has a smaller fan and lower thrust rating. In contrast, the twin-engine 787 Dreamliner is fitted with the more powerful GEnx-1B variant. This engine commonality allows airlines operating both aircraft types to streamline maintenance procedures, spare parts inventory, and technician training, leading to significant operational efficiencies.
Official Source: https://simpleflying.com/true-boeing-747-8-787-dreamliner-powered-by-same-engine/