Depending on the engine, always keep the RPM's down for the first 10-20 minutes until you reach a nice core temp, very important on our old Harleys during break in, and everyday when running, we try to keep it under 50 for the first 10 miles, lets everything metal, expand to it's full size, and cuts down on wear and tear, so I've heard ... must work, I've got 62,000 miles on the softail!