A fuel injection system is a mechanism in a vehicle that injects fuel into an engine for combustion. Some of the synonyms for a fuel injection system include electronic fuel injection (EFI), gasoline direct injection (GDI), common rail direct injection (CRDI), sequential fuel injection (SFI), and multi-point fuel injection (MPFI). EFI is the most common type of fuel injection system used in modern cars, and it uses electronic sensors to determine the optimal amount of fuel to inject into the engine. GDI was introduced in the early 2000s and allows for more precise control over fuel injection. CRDI is commonly used in diesel engines, while SFI and MPFI are older technologies that are not as efficient as newer systems.