I have drawn the “really” ? quote here for being an advocate of an early oil change with a new vehicle … yet on a rebuilt motor … some done with the attention to detail that Clinebarger displays … it’s a ritual to do a short run and dump the oil.
What is the main difference in these two ?
The reason I like to dump the oil soon with a new engine is because you will always have very small metal particles in the oil of a fresh engine. No matter how well you machine the parts, and how well you clean them prior to assembly, there's always going to be some microasperities that get knocked off the moment the engine is fired for the first time. Many of these particles are
As far as the engine's break-in, about 90% of it occurs in the first 10 seconds after you start it up for the first time. The rest of the break-in is getting that last 10% done, establishing anti-wear tribofilms where they need to be, and ensuring uniformity for maximum life expectancy. This is achieved with varying rpm and load over several heat cycles.
For OEM engines, a test fire in the factory takes care of that 90% and the engine is usually solid enough to last well past the warranty period. They aren't as concerned with getting that last 10%. For someone like me, who is OCD when it comes to pulling every last 0.5 hp possible in reduced friction and efficiency, that last 10% is vitally important. It's the difference between an engine that will be competitive in its class and one that won't even qualify. It's the difference between an engine with 3% leakdown and one with
Friction modifiers and viscosity modifiers both reduce friction in mixed lubrication, reducing the shear stress on the oil film itself, which actually reduces the reactivity of ZDDP. This is the same reason PAO base oils aren't recommended for break-in. Shear stress and friction are excellent drivers of ZDDP reactivity, and when you have a fresh engine with no ZDDP film established, getting it activated as quick as possible is important. Detergents can interfere with ZDDP at high concentrations so you only want enough to keep down acidity during the short break-in. Driven BR30, for example, is ~2800 ppm Zn, ~2600 ppm P, ~300 ppm Ca, 0 ppm Mg, and 0 ppm Mo in a straight 30 grade base oil. The type of ZDDP is also a less stable / more reactive secondary alkyl ZDDP to ensure fast reactivity.