The aim of this work is to highlight theoretically and experimentally the effect of cyclic speed fluctuations on the temporal and angular deterministic parts of signals recorded on rotating machines operating in steady state conditions. The deterministic parts of such cyclostationary signals are defined by their periodic components, or their CS1 part (order 1 of cyclostationarity). It can be assessed by using cyclic averaging, using a time or angle sampling, leading to an estimation of the temporal or angular deterministic part. If the instantaneous speed of the machine is not purely periodic, the temporal and angular deterministic parts will be different. These differences are firstly theoretically considered, and then experimentally assessed in the case of a diesel engine.