The 2.5 generation was developed to meet Euro 5 emissions standards and can operate at maximum pressures of up to 2000 bar. These injectors feature improved injection characteristics, including an enhanced Injection Rate Coefficient Factor (IRCF), enabling up to seven openings per injection cycle and providing protection against dirt ingress into the injector body. Other components remain similar to the previous generation, but the needle and its seat are coated with a special finish to enhance injection dynamics; the seat angle is now 60°, and the needle diameter has been increased. The angle between injector orifices has been reduced, while the inlet port diameter has been enlarged to allow a higher volume of fuel. The return spring preload is 28 N, and the injector body diameter increased from 17 mm to 19 mm.

There are two possible connector types: for example, systems like JCB or DAEDONG use connectors similar to DFI 1.1–1.3, while other brands might use DFI 3–type connectors. The return flow connector may be either metal with a rubber nipple or plastic. These injectors function similarly to DFI 1.5 units and are factory-calibrated using the C3I method and assigned a 20‑digit code.

The DFI 2.5 HPI variant is designed for large engines in Euro 4 and higher-equipped units, operating at pressures up to 2000 bar. These injectors have notably large body diameters (26 mm or 28 mm) and enlarged inlet openings. A distinctive feature is the unique connector: since the injector is located deep in the cylinder head, only a wire connected to the vehicle’s main wiring harness is exposed externally. The connector penetrates deep into the engine and connects to the injector in its middle—an unusual arrangement driven by use on very large engines. Likewise, the return flow channel is located centrally within the injector and connects to internal passages in the engine head.