In the shop we only sell engine flushes on the new 112, 113 motors when they begin to consume excessive amounts of oil. When the FFS intervals get ignored the engines begin to carbon up the piston rings leading to oil consumption. If flushed before the bores get beat they usually can return to service without issues.

As a preventative maintennace it's complete overkill. I wouldn't drive the car with it in the oil either. We run the car for 30 mins in neutral @2500RPM to flush them. The stuff is meant to thin the oil and dissolve gunk, not support your bearings under load.