Hopefully the harmful particles from engine break-in get trapped in the oil filter. If not, do most of the remaining harmful particles flow out the drain (suspended in the warm oil) when performing the vehicle’s first oil change? Or, during the oil change, do untrapped harmful particles sink and remain in the bottom of the pan (which is unable to drain completely)?
No real need to even wonder. Old shop theory was mostly a bunch of stories. You will find lots of stuff in oil pans over the years. It’s the gear teeth that drain out of a manual transmission that make me wonder.
I don’t believe you will find any significant pieces of metal to drop to the bottom of the pan. Any oil pans I’ve seen well after break-in (300K) contain maybe only powdery residue that would either flow out with the oil, be caught in the filter, or sink to the bottom of the pan and harmless.
Guess I should check our oil level after 1st change. Dealer did inspection. Said new car looked good. No leaks. So I assume the oil they added is still in motor.
Engine building process has evolved over the past 50 years. There are little if any particles in the oil of a new engine…and there are ZERO particles that can do it any harm.
Given that oil filters trap particles larger than about 10 microns (some filters down to 5 microns) or 0.00004 inches, any big chunks that get sucked up by the oil pump won’t get farther than the filter. A good oil will suspend the rest. Since the bearing gaps are in the 0.0015 inch range, the 0.00004 size particles just pass right through.
The junk you might see in the pan or on a magnetic drain plug are just slivers left over from the assembly process. Mostly non-existent in new cars these days.
@Mustangman I agree. Assembly processes are so squeaky clean now that there is little or no harmful debris found in a new car. On the other hand if you let a shop rebuild your engine there will no doubt be some debris and an early oil and filter change will be in order.
The last time I had internal engine work done (rings and valves) was in the summer of 1964 on a 1957 flathead Plymouth engine. That “overhaul” cost me all of $65 at the time when $5 would fill the tank with regular. Since the rest of the car was starting to rust I told the shop not to “rebuild the engine”.
I agree, but would add that oil’s biggest enemies are dilution from blowby, that being combustion gasses that blow by the rings when the explosion happens, heat, which is why engines with turbochargers require synthetic (it stands up to heat better), and a breakdown called “shear”, which is actually mechanical damage to the oil molecules. Particulates get trapped and/or drained, but these other enemies just build with use.
The way oil functions in the engine isn’t well understood by the average car owner. It cleans, removes heat, maintains a pressurized fluid barrier between key sleeve bearings and their corresponding surfaces, and also provides an unpressurized fluid barrier for the piston rings to slide on the cylinder walls. I suspect the average driver only thinks of the last function as oil’s only job.
@mountainbike Agree that oil fulfils several functions. This was explained to us by an army instructor when I did Motor Mechanics. When he asked if their were any additional comments, I put my hand up and said that oil also really quiets down the noise in a gearbox. That benefit he had not thought of.
LOL, I like that one Doc. I never would have thought of it. 
@Docnick I’ve built several engines myself over the years. No matter how much de-burring and cleaning and care I’ve taken, I always get a slivers on the magnetic drain plug. One short oil change and it all goes away but still, how do manufacturers get them so clean these days?
If you had the facilities, computer-run CAD/CAM machinery, process engineers, methods engineers, chemists, metallurgists, machinists, prototype runs, “first article” trials, process validation trials, design software that costs tens of thousands of dollars a pop, etc. etc. etc. that the major manufacturers have, I’m sure you could produce pristine near-perfect engine parts too. 
I put my hand up and said that oil also really quiets down the noise in a gearbox.
You reminded me of the brand new Maytag washer I had that belched out every drop of gear case oil onto my basement floor within a week of buying it. The repair guy comes and says they probably will not authorize a warranty repair because- the oil is only there to keep the unit quiet.
Seriously? What makes you think I don’t want my brand new washer to be as quiet as designed? Not to mention the lack of lubrication…
Just put in some sawdust. I guess that didn’t work out so well for Barney…
I had the pleasure of designing some factory test equipment for small engine manufacturers. They test each and every engine that comes down the line. Automated equipment grabs the engine as it rides by on a trolley system, adds gas and oil and runs the engine. Electronics monitor the performance and ensure it performs as intended. Afterward, the engine is tipped in a way that promotes draining of the lubricants and gas into separate troughs for filtration and reuse. Not sure if the auto engine folks do similar but would make sense. The assembly plant does not want an untested assembly like this being installed and then have issues requiring it to be removed/stop the line etc…Any contaminants would be flushed out by this initial run in.
In addition, there’s the parts cleaning.
Many years ago I worked for a company that made pumping systems for military potable water trucks. We had huge agitated cleaning baths, the cleaning being a multistep process, that were regularly monitored by in-house chemists for ph, temperature, and all the other characteristics necessary to ensure the effectiveness of the chemicals and cleanliness of the parts. Parts were moved by a gantry crane from bath to bath. They remained in each bath for a specified time. No small shop can match that, or should feel it needs to.
Interesting about the small engine testing. Mentioning Maytag, I’ll go a little off topic for a minute. We needed to replace our central air unit and one of my questions was where it was made-US or not. Also who actually makes it. Talk about a jumble of buying and selling trade names. Bought out a couple times by investment groups, then the trade name licensed to someone else and so on. Unless you can drill down to the actual plant doing the work and where the components come from, brands just simply do not seem to matter anymore. I guess warranty and local support are the best solutions and maybe increasing the budget to cover more frequent replacement than before. Carrier going from Indiana to Mexico is now off my list, rightly or wrongly.
Pick your brand, Skill, Porter Cable, Ford, Chev? Gotta be the same plants supplying parts to everyone. Not like the days that Ford controlled everything from castings to window glass. Rant over, but when someone says they prefer LG to Maytag to Whirlpool, etc. it would be really interesting to actually know the source of all the components. And I’m convinced there are only a couple of folks making car interiors. Otherwise, why are they so similar? Like the GM guy said, they are really just assembly plants now.
Because the interior componentry (or any other componentry) is manufactured by vendors does not mean it isn’t designed by GM (or Ford, or whoever the major manufacturer is). Outsourcing to approved vendors using specification control drawings (or, in many cases, source control drawings) is normal in the manufacturing industry.
@bing, you remind me of working in TV repair shops in the mid '70’s.
Brands like Zenith, Admiral, RCA really meant something.
Different design approaches; and definitely higher quality than some others like Magnavox or GE.
Even the lowbrow Muntz had its unique charms.
Many (edit: of those companies)are still around, but bear no resemblance to their heyday.