The engines from the factory are NOT broke-in. They are indeed run and tested and yes also driven to a truck or train for deliverer but they are NOT broke-in ready for hard use.
I don’t recall where I got the following information but it was some time back and I saved it to a Word document for future use. This seem an appropriate time to share it:
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Engine break-in information:
Breaking in an engine is a process of properly wearing-in the pistons/cylinders/rings, bearings, valves, camshaft, lifters, rockers, etc... In addition, part of the breaking in process is not only wearing-in and seating the internal engine components but also stress relieving the components as well. Crankshafts, connecting rods, pistons, blocks etc... have many stresses due to the casting or forging process, machining and welding process.
These stresses are properly reduced/eliminated by costly and time consuming heat aging as well as shot peening and or high frequency vibration on a very specialized bedplate for an extended period of time. For production applications this is cost and time prohibitive. Therefore, the next best thing is exposing your engine to multiple heating and cooling cycles under various load and RPM's. The heating and cooling break in process continues over a period of time.
Further heat cycling break-in will continue during the multiple heating and cooling cycles from driving your vehicle under varying RPM and engine load conditions and then shutting it down for a long period of time to let it cool completely. The multiple heating and cooling cycles are an extremely important factor in properly breaking in a new engine and are often an overlooked factor in the total break-in process. These heating and cooling cycles achieve what is called stress relieving. Back in the "old days" of engine manufacturing, after casting and before an engine block was machined, it would be set outside for several months to age, during which stress relieving occurred naturally, then the block was machined, which helped to produce a better engine than one that was machined immediately after casting.
By changing the factory installed oil and filter after the first 500 miles you will also be removing the initial wear-in particulates present in the oil and filter. The reason for this is that during initial wear-in there is very high particulate contamination in the oil. These particulates consist mainly of microscopic particles of aluminum, bronze, copper, lead and iron, plus soot particles and other by-products of combustion in your oil. Your filter cannot filter out all these small particulates as many are sub-micron size and too small for the filter to trap, BUT they are also small enough to fit between your bearing and other internal clearances and cause wear. That is why we recommend to that in order to properly break-in a new engine, regardless of what your new car salesman or dealership personnel tell you, is to perform the first oil and filter change at 500 miles.
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It is never a good idea to take a new vehicle, or more specifically, a new motor out and drive it like you stole it because you are only taking life out of the motor. Ask any “professional” engine builder that builds motors for long term and they would tell you the same thing. Break-in is the most important aspect of the longevity of a motor…