Derating sometimes is done intentionally when you want to prolong the engine's life and avoid substantial wear or damage. However, in some applications, such as a power generation facility, unwanted derating reduces the energy production which leads to lost revenue potential.

What causes a diesel engine to derate?

A derate is designed to protect you from causing engine or DPF damage. A derate can be caused by various sensors or systems. However, when it's a specific 5 MPH derate then you can be certain that the problem is related to the emissions, aka the aftertreatment system.

What is derated diesel?

marine. The operation of a diesel engine at normal maximum cylinder pressure for its continuous sea service rating, but at a lower mean effective pressure and shaft speed.