Break-in New and Rebuilt Engines
Your engine is a mechanical device with medal parts attempting to work in concert with other medal parts. The better these parts work together the more efficient the engine will run. When you engine is new or just rebuilt those medal parts have yet to completely "seat" with each other. During the initial hours of operation fine metal shavings, sometimes smaller than the human eye can see, will develop and make its way into the oil pan to be circulated throughout the engine. Over time these shavings of metal can cause premature wear.
During the first 4-6 hours (200-500 miles) of the engines operation it is best not to drive it to the extreme, moderate you driving habit. Avoid hard acceleration and quick variences of speed. It is not a good idea to tow anything during this time. Once the break-in period is over, change the engine oil - this added expense early on may even double the life of your engine which makes it well worth it.
