Originally Posted by Jimmy_Russells
Here's the thing I don't understand:
I see there's some metal in the filter in the original post, that's obvious. But, the metal has already travelled through the engine and been captured by the filter. Any damage it would do has already been done, and it's not going back into the engine. Even if you change the oil now, any new metal particles that are created are going to also travel through the engine and get caught by the filter, again. I don't believe draining the original oil is going to have literal chunks of metal debris flowing out with it. If the oil does have remaining micron level suspended metal particles (no doubt it does) that are small enough to travel through the filter, they're not going to be large enough to cause any damage.
Of course anything large enough will be immediately taken out and will never be recirculated unless there's a tear in the filter or a bypass event. I don't necessarily buy it, but the supposed rationale is that metal particles that don't get filtered out still have an affect on wear, and the additional rationale would be that it would be beneficial to limit the amount of these particles by dumping the oil early.
A lot of marketing of bypass filters is that particles as small as 2 micron can cause damage, and that getting those particles slowly filtered out can nearly eliminate one source of wear.
I did a few early UOAs on the last new car I bought. Of course the filter will trap anything large enough, so large shavings wouldn't typically show up in an UOA unless they settle at the bottom of the pan and end up in the oil sample. The aluminum levels were actually pretty normal. There was elevated iron and copper, which is probably from cam break-in. However, these particles were likely recirculating in the oil, and depending on who you ask that could mean elevated wear compared to getting rid of that as soon as possible.
I remember the talk about 3000 mile oil changes was primarily a suggestion that additional wear occurs because the oil is dirty, as opposed to loss of viscosity and depletion of additives. So I suppose the claim is that during break-in it gets exceptionally dirty due to elevated metals, so it would be good to eliminate as much of that as possible.