"Bearing surfaces, for example, need to form a match. If the bearing is overloaded during this break-in process, galling might result, which can shorten bearing life or, in the worst case, cause a seizure. Valves must seat in the head and rings must wear in to form a good seal against the cylinder wall. Otherwise leak-down will be excessive and the engine will never be able to reach its maximum performance. For best results, rpm should constantly be changing, with no long runs at a fixed throttle opening. It is also very important to make the first oil and filter change at 600 miles to remove contaminants that could later cause excessive wear."