Idle speed or slightly above, maybe 750 RPM or so, won't hurt most engines as long as no driving load is applied. I'd suggest a somewhat longer flush time, maybe 15 minutes or so, then drain, change the oil and filter, and drive on. I'd be a little reluctant to do the same thing with a trans or rear end, unless you've got the rear wheels off the ground where nothing gets driving loads applied, even for a short trip.
Jerry
