Changing/Replacing Lube oil


We have GE gas turbine frame 9E and we are going to change the lube oil. already it was Shell turbo CC 32 and we want to change it to Shell turbo S4 GX 32. It means same viscosity.

Is flushing needed before injecting new oil? We didn't have any crack and major issue, just cause of oil quality we are going to change.