Oil analysis is good to check the state of the oil NOW. To use it as a tool to determine oil change interval you’ll need to keep doing it throughout the life of the engine because over time/use engine parameters change and thus the calculated oil change interval will change (shorten).
I applaud the work from an engineering point of view. But I know if I change my oil every 5k miles I can keep my engines running good for well over 300k miles. Proven that several times. And my town likes that because they heat the DPW buildings with used motor oil.
I did not ask for anecdotal opinions, nor life recommendations. “Oh, and speaking…” What more opinions. I am looking specific facts and evidence, but it appears you are intent on hijacking this discussion.
I am not responsible for how you choose to interpret, or what you infer from my posts. Good luck you seem capable of finding the evidence you seek on your own.
The read I am getting from the OP is an angry GM owner looking to collect “evidence” for his lawsuit against GM for this travesty of an OLM. The OP may even think we are paid to answer his questions.
I suspect there is a “Get off my lawn!!” Comment lurking around waiting to be posted
This is totally uncalled for…
I have nothing against engineers, heck, some of my best friends are engineers.
One engineer friend found himself unemployed about 4 decades ago. I was helping him with a project and I noticed an ad in a local newspaper in a rural area where we lived. The ad was posted by a major utility company. It was to attract engineer candidates for position of Nuclear Power Plant Operator.
I said to my fiend, “Hey, Bob [name changed], look at this! These guys want to hire an engineer and you need a job.” He thought that he wouldn’t qualify, as he had no experience in that field, but I was more confident and stayed on him for several days. He finally, somewhat reluctantly applied. He is very personable and exhibits an impressive stature and was promptly hired and made an entire lucrative career operating that plant until his retirement time came and the life of the plant had reached expiration and he was instrumental in decommissioning it.
Anyhow, long story longer, back when he applied he was driving a bright yellow Toyota Land Cruiser. It looked like one of those darn safari vehicles. He (he was a rather large man) loved that machine (well engineered?). He made just regular oil changes, nothing special, and the vehicle ran nearly forever.
Anyways, although I can’t provide the specs that are being sought, I thought you’d enjoy my engineer anecdote and a view of how a “brother” engineer, nuclear power plant operator, handled concerns about oil changes and oil cleanliness, while you await their arrival.
Getting back to your original post, modern OHC engines do retain a bit of oil in the heads. Most will have the cam(s) sitting in a bath of oil so that lubrication of the cam lobes is immediate. That wasn’t necessay in the old OHV engines because the cam is a lot closer to the oil pump and gets oil a lot quicker than the OHC cams.
It is a double edge sword, it retains oil to protect the cam, but it also prevents a complete drain during an oil change. It does seem to me that a 15% retention is a bit high though and I’d wonder if the oil drain back holes are getting clogged.
There is also the issue of the anti-drain valves in most oil filters, especially in side mounted filter and top mounted filters where the filter openings are pointed down. They would hold oil for some period after shutdown but in most cases will drain down overnight. But since most only hold about a cup of oil, that would account for about 5% of the oil, and 0% when the filter is removed.
I read an article from Blackstone labs years ago, I don’t have it anymore, about dissolved metals in oil. During the first 3k after an oil change, dissolved metals build up in the oil and actually increase the lubricity of the oil. The oil stops absorbing metals after this point and wear decreases to its lowest point. It remains low until the breakdown of oil, which goes in stages, reaches the point of creating abrasives through coking. Coking occurs after the oil thickens to sludging stage. The ideal is to change the oil just before the sludging stage or before the detergents and other additives are used up.
An oil change, even if only an 80% drain “kicks the ball down the road” so to speak. The fresh oil and additives extend the life of the residual oil. The little bit of retained oil with dissolved metals will kickstart the increase in the lubricity of the fresh oil.
My take on this is that unless I have inherited a badly abused engine, I would not do back to back oil changes, but rater shorten the oil change interval if needed to adequately protect my engine.
BTW, I’ve been rebuilding engines since the early 70’s and typically only give up a vehicle before 200k miles if it has been totaled in an accident.
Per wiki:
" The F engine block, crankshaft and lower end assembly is loosely based on the 1939-63 G.M.C. L6 OHV 235 engine but with a taller deck (rather than the similar but smaller Chevrolet 1937-63 Gen-2 L6 OHV engine), and built under license. The cylinder head and combustion chamber is derived from the Chevrolet L6 OHV “stovebolt” engine, slightly scaled up. The general idea was consumers would feel comfortable with the engine since it was a familiar design and had a proven track record. None of the bottom end of the engine is interchangeable with these engines.
The F engine replaced the early 3.4-liter B gasoline engine introduced in 1938 (not to be confused with the 2.9-liter B diesel engine introduced much later). The early B engine was based on the original 1929-36 Chevrolet Gen-1 207 inline-6, not the later 1937-1963 Gen-2 216, 235 etc. engine."
How do we avoid threads like this, where an often new poster shares his work/investigation/questions, and the discussion ends up being less than respectful?
None of us intend for it to start out that way. And I suspect none are happy it ends that way.
There hqve been two comments about my insomnia lately
/. I don’t really have insomnia. It is just that as a trucker, I lived almost my whole kife without a schedule. For much of it, I was on call 24 hours a day, 7 days a week. The phone would ring and I would have two hours to report to the terminal. If I was too sleepy tp work I was supposed to call the company and go off duty for eight hours, but I had to do that before they called me. That would have dropped me down the call board to the bottom and usually meant missing two days work with no guarantee that I would not be tired the next time they called.
Sine I retired, I go to bed when I am sleepy, and get up when I wake up. I may go to bed at 9 pm or 4 am and I sometimes get up at 5am.
It never occurs to me that someone will have a notification sent to their phone when I post and then keep that phone on and next to their bed and I don’t understand why they would.
As far as the OP, he seem to be trying to solve a problem that doesn’t exist. The only cars I ever lost an engine on were from broken connecting rods while racing. I have never worn one out and his suggestion to change oil twice in succession Is ridiculous when we are trying to conserve oil. He has a car with a quad 4 that isn’t a grocery getter???
I knew that was possible and some people did it . Just one more thing to put on my list of things I don’t understand . The only call I want after dark is from the automated Tornado warning system.
I have observed, read, and discussed as well, and completed my own testing to back up that up. I have come across others who have claimed there Automotive Engineers from BMW, who hide behind fake names, and tout credentials. They claimed that 99% of the total oil volume in an an engine drains in a normal oil change, but could not back it up.
I have no doubt that On-Star collects information, but in the end it is only projected model they come up with. GM does not have good track history with their OLM system and have had to update them several times in various models. My current calibration is recommending 7k change intervals when oil analysis is showing it is falling out of spec by 3k.
“Most people forget their oil changes.” Do you have any evidence of that. That is a lot of consumers. Define delay? Most people I talk to on these forums change their oil before the OLM recommends it. Until these OLM monitors viscosity and particulate counts, they are only an educated guess.
Why would any manufacturer put a filter in a transmission that requires complete removal of the transmission and cracking the case to change it. Magnets only help a little, there is a lot of non-ferrous material in a transmission.
Surely a so-called former GM engineer could provide some credible sources of information,
