Most people never come to these forums, rarely keep a new vehicle far beyond the factory warranty or yet beyond 10 years and only care about when the OLM tells them to change and where the best price on the next quick oil change. My method is directed at enthusiasts and those wanting to keep their vehicles for long periods of time.
Which is why I specifically mentioned those livelihood applications where the most mileage is accrued.
My wear rates are often 1.5-2x higher when I leave 15-20% of the old in after a spill and fill. I have seen my fuel dilution start off at 1-2% when I do not flush the old oil out and at levels above 4% I see a similar increase in wear. I have seen my iron wear levels start off at 5ppm rather then 0 ppm when I leave the old oil in. That residual wear metals do have an affect on future wear. The viscosity thins out much quicker, and TBN is reduced much quicker when I leave the old oil in.
I think you are conflating wear-rate with residuals from the previous fill. Of course if you don't get all the old oil out those numbers are not going to start at zero. The fact you can measure them however means that all of that is in suspension.
My wife and I follow different oil change methods. She changes every 3k miles in all her cars, with the current recommended API oil that is available at the most convenient oil change service center.. Her car is mechanically sound with no oil consumption, and no fuel dilution, mixed driving and 180k miles. Her camshaft cover and valve train has heavy varnish and deposits. I run 2-3x longer drain intervals, with high fuel dilution and premium synthetic oil and Full Volume oil changes and my valve train has zero varnish and sludge and looks like new at 150k.
I'd suggest cruising through some of the pics that have been posted on here over the years.
This was the S62 in my E39 M5. It has what we would all consider an extremely complex oil system. Dealer oil prior to my acquisition, this run was on M1 0w-40:
OCI length I ran was 10-12,000Km (6,200-7,500 miles). This picture was at ~100,000 miles.
This engine fuel diluted like mad, being high performance. As you can see, that didn't result in varnish formation.
How does one know when when the dispersant and detergents holding capacity or threshold is reached. I rarely see much of change in additive levels even when I triple my OCI. Oxidation and nitration only increases small amounts. The dispersants do not help with fuel dilution or wear metals such as iron, aluminum, lead, tin and other metals correct. I think they have some affect on free copper from coolers based what I have read.
It should track with the depletion of the TBN in the oil for the most part. The compounds used to neutralize acids are the same ones used to keep contaminants in suspension. And yes, these help with the wear metals (that's why you can measure them in your UOA) while fuel is just a diluting agent (thinning primarily, though it does work to degrade the oil as well).
Some polar bases, like esters, will chelate copper from oil coolers, I think that's what you are thinking of there.
I would like to see some actual comparative studies between short volume oil changes vs full volume oil changes with respect to wear rates, and lube performance with both normal and extended drain intervals. Many interested parties would cry at the thought of the so-called wasted oil with FVOCs.
@Doug Hillary did extensive fleet tear-down testing of some 500HP Detroit Diesel engines run on Mobil Delvac 1 5w-40 in the Australian outback. OCI's were around 100,000Km, he used centrifuges to control soot loading. There were pictures posted on here from a 1.2 million km tear-down (~750,000 miles) where the liner and bearings measured "as new" and were returned to service.
As I noted previously, the highest mileage vehicles are typically OTR trucks for diesels and courier/taxi/limo service for gas engines. The million mile Ford van was I believe a courier.
The problem with what you are requesting is that nobody operating these fleets of vehicles in service conducive to accruing that type of mileage is going to intentionally waste oil for the purpose of this experiment unless somebody else was footing the bill. If a taxi fleet is able to get 500,000 miles out of a Modular before the valve seals are shot and it starts fogging blue, there's little incentive to double their lubricant use just in order to reach that same milestone.
I'd also expect that if there were merit to this approach you would have seen the oil companies pitching it (double consumer oil use?! sounds like a profit windfall!) but they don't. In fact the focus more recently has been on more expensive oils able to be run longer (M1 AP and EP for example) and testing of this duty cycle (Mobil's taxi test).
Wynns Corporation that makes coolant and transmission fluid exchange machines and used by GM dealers also made an engine flush machines that uses clean oil . I have seen these services in Japan and Korea when I lived there.
And Japan is also the place where engines are retired early and sent over here (JDM import engines, in varying condition). I'm not sure that's a great benchmark, referencing a market where achieving high mileage is almost unheard of
And yes, it doesn't surprise me that a company that makes flush machines would make a flush machine targeted at oil as well.
It never took off or was adopted in the US, because so many believe all the oil drains into the pan upon shutdown, and the minute amount still in the engine has no affect on the new oil or engine. My first engine I rebuilt was a Ford 289, much different design and a lot of oil would drain. These new engines with VVT, DOHC designs, turbos, coolers retain far more. I have looked and have not seen any comparative studies, but I do agree with Machinery Lubrication articles on residual oil and short volume oil changes, and their affects, as I have seen similar affects in my own vehicles.
Lots of experience with Windsors here as well, though primarily 302's (currently have a GT-40 351W in a '95 Supra Comp TS6M). The EFI 302's were quite prone to having the PCV screen plug-up, resulting in a loss of crankcase breathing, often leading to significant accumulation of deposits in the valley, even if run on quality oil. I had a high mileage 302HO from my '87 GT that was pristine at ~340,000Km (~210,000 miles):
This was another 302HO, we picked it up as a low mileage donor for a car my buddy bought, not high mileage (probably around 60,000 miles?) but M1 0w-40 was keeping it clean. 1st car we put it in (carb, Vic Jr.):
Same engine, 2nd car, a couple years later:
Then there was this fun 302HO swap into a clearly abused '90 F-150:
Old engine, obviously not well maintained:
Donor Mustang engine, had ~150,000Km on it (100,000 miles) IIRC? Run on AMSOIL:
We can probably agree that keeping the oil clean and for longer periods, improves performance, improves oil performance, reduces wear and extends the life of the equipment. I do full volume fluid changes on my transmissions and they have all lasted 250k miles or more.
Sure, a high quality oil changed at reasonable intervals using an efficient filter is my go-to, and has worked for me. That said, I've seen enough pictures on here of engines owned and operated by people that don't go to the same lengths but still stay clean that I'm hesitant to paint with too broad a brush. Duty cycle is clearly a huge contributor, as is engine design. The Honda VCM V6, pictures of which
@Trav has posted, is an engine that will readily produce copious amounts of build-up when maintained "normally". A Modular in the same service would stay clean. This is just due to the design.