Components of Diesel injection systems are often autofrettaged, to achieve the necessary fatigue strength by introducing residual compressive stresses. The fatigue assessment of such components is rather elaborated for room temperature conditions. However, the maximum operating temperatures are at 180 °C in heavy crude oil engine operation mode. The influence of this elevated temperature on the fatigue strength of injection systems is examined here for the first time experimentally and analytically. Methods based on the theory of plasticity and fracture mechanics have been applied. The fatigue strength prediction was successfully validated using experimental data obtained by testing specimens with crossing bore holes.