How did I know that bertsmobile1 would post a scientific response!
Back in the 60s Exon came out with Uniflo 10W30 detergent engine oil. According to Exon, this was the final answer to the best engine oil ever. A lot of automobile service businesses started using this oil in customers cars. Back then not many engines had full flow engine oil filters as most had the 10% filters. Many engines of that vintage had hydraulic valve lifters and the first indication of the use of Uniflo 10W30 oil was clacking valve lifters. As time went on and some mechs wanted to find out what was causing the lifters to collapse, they found that crud that had been loosened up by the detergent engine oil had plugged the small holes in the lifters where oil under pressure supplied the lifters to keep them pumped up.
Castrol multi-viscosity engine oil was another source of this problem. Having been a member of the Service Managers Association in the 70s and 80s, we would get together and swap stories. There were folks from power equipment, marine and automotive businesses attending these meetings.
I have some knowledge of air cooled engines having been an aircraft mech for many years and dealt with small opposed four cylinder 65 HP Continentals to 28 cylinder, four rows of 7 cylinders on Pratt & Whitney R4360 3,500 HP radial engines, both dry sump and wet sump and aerobatic sumps. I also dealt with turbine engines when the change over to synthetic engine oils was going on. Also hydraulic systems were changed over to fire retardant synthetic fluids. We had to deal with all of this as mechs and it wasn't pleasant.
I'm done, I gotta get to work on some power equipment and make some billable hours!!
I still love you my fellow wrench brother and always look forward to your posts!
Yes it was a problem with engines that relied on debris settleing out and forming a sludge suddenly having all of the contiminants staying in suspension.
IT is staggering just how much of the solids just stick together & drop to the bottom of the oil tank or sump.
However the story is still the same the detergent is not cleaning the engine as the TV adds suggested, it is just stopping the crud falling out of the oil and sitting in the bottom of whatever was used to collect the crud.
Hydraulic lifters would be a horror story because the entry hole is tiny.
The set up is exactly the same with BSA engines because the internal crankshaft filter was supposed to be cleaned out every 30,000 miles with the sludging mono grade oils .
This final filter was only ever designed to catch the stuff that did not form a sludge in the bottom of the oil tank , probably 5% to 20% of the total particulate contamination.
Suddenly it trapped 100% of all of the particulates and would block solid in as little as 10,000 miles thus the left side big end got little to no oil and got really annoyed so jumped out of the engine.
I have pulled apart engines where the sludge is packed in so hard it had to be drilled out with a very sharp wood drill because standard metal drills went blunt in a few minutes.
The manual tells you to hook the end of the basket with some wire, pull it out and reverse flush it.
So the problem you had then was idiots running their cars & trucks on a type of oil it was not designed to run on.
Back before spin on oil filters we used to drop the sump every couple of oil changes and scrape the mud out of the bottom as the sumps were deeper and used as sludging tanks,
Same story for tappet adjustments, part & parcel of this was manually washing the accumulated sludge from the inside on the rocker covers.
These build ups of "mud" were intentional and part of the lubrication system.
Once detergent / dispersant oil came into popular useage, this crud was still made by the engine, the only difference was it was supposed to be caught by the oil filter as finner particals not big blobs of sludge.
Ashless oils do not form anywhere as much sludge because they do not "burn" ( oxadize ) to the same extent as regular oils and can take a lot higher temperatures.
Prior to synthetic oils becoming popular most of the "ashless" oils came from Australia as our crudes contain no sulphur , no phosphorus and have the lowest ash content of any crude on the planet.
Thus we would export crude to the USA for refining into lubricating oil while importing crude to be processed into petrol because our crude made very low energy petrol because it has fewer volatiles ( which is why it has such a low ash content ).
The widespread adoption of synthetic oil for lubrication is the driving force behind the closure of all but 2 of the Australian Oil refineries as what our oil was desperately needed for ( mostly avaition oils ) no longer existed so we could not get premium prices for it.
As an aside that is the same reason why we export so much coal as just like the oil our coal deposits have the lowest Sulphur content ( no acid rain from burning it ) low Phosphouous and very low ash while having the highest coke crush strength ( good in blast furnaces & cupolas ) .
However I have ranted on for way too long.
The only point I really wanted to make is it is not the detergency that was causing the problems with bed in and "DETERGENTS DO NOT CLEAN" they are nothing more than an aid in transporting muck away which of course can & will end up depositing in all sorts of places where you don't want it to if the engine was designed to run on a standard oil.
I am no oil expert but I had some riding companions who were, but part & parcel of one of my degree was a short course on oils explaining what they were, what they do & how they do it. What was added, why it was added & how it worked.
Unfortunately this is missing from most certificate & diploma automotive engineering courses which is jhow advertising agencies get away with twisting facts into lies and confusing the public at large.