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-   -   A Look at GM's Oil Life Monitoring System (http://www.camaro5.com/forums/showthread.php?t=145143)

franknbeans 05-03-2011 10:52 PM

A Look at GM's Oil Life Monitoring System
 
I read this post on another forum at www.bobistheoilguy.com

Good read on the "Big Bird" break down of the oil life monitoring system.

Quote:

One thing I can touch on and clear up.....the GM oil life monitor operation and my statement that ZDP (or ZDDP as you tend to call it here...most of the API literature just sticks to ZDP so I tend to use that) depletion is the basis for oil deterioration.

My spelling is poor but ZDP stands for zinc dialkyldithiophosphate which , as it sounds, is an anti-wear compound comprised of zinc and phosphorus.

ZDP is dispersed in the oil so as to be at a potential wear site if a surface asperity happens to break thru the oil film thickness causing the dreaded metal-to-metal contact. A molecule of ZDP must be present at that moment to prevent microwelding at the contact site which will cause material transfer, scuffing, scoring, wear and catostrophic failure. The concentration of ZDP in the oil will determine if there is ZDP present to work it's magic. The greater the concentration...the more likely a molecule of ZDP will be there...and vice versa.

By nature, ZDP is sacrifical. As ZDP is "used up" at a wear site to prevent micorwelding the concentration of ZDP decreases.... So...if you measure the ZDP concentration in engine oil in a running engine it will decrease at linear rate based on engine revolutions. Any given engine has a certain number of high potential wear areas where metal-to-metal contact could occur due to reduced film thickness and/or surface asperities....areas such as rubbing element cam followers, distributor gears, rocker arm pivots, push rod tips, etc...... The more of these areas the more ZDP depletion. The more often these features come in contact the greater the ZDP depletion. That is why, generally speaking, ZDP concentration in the oil, for any given engine, will decrease at a fairly linear rate when plotted versus cummulative engine revolutions. The more times it turns the more contact the more chance for wear the greater the depletion. This is as much of a fact as I could quote ever and is really not speculation or anything. It is proven beyond a shadow of a doubt in many studies. That is why it is ONE of the basis for determining oil life remaining and why it is THE basic premis of the GM oil life algorithm. It is only ONE of the things that determines oil life...but it is the one thing that can be tied to engine operation in a linear fashion and estimated very accurately by accumulating engine revolutions via a counter.

The GM engine oil life monitor counts engine revolutions and accumulates the number for the basis of the oil life calculation. It then adds deterioration factors for operating temperature, start up temperature, soak times, ambient, coolant temperature, etc... There are a LOT of factors that "adjust" or affect the slope of the deterioration but the fundamental deterioration is traced back to the ZDP depletion that is inescapable with engine revolutions. The specific rate of ZDP depletion is readily measurable for any given engine so that is the fundamental item that is first calibrated for the oil life algorithm to tailor it specifically to that engine.

You would obviously like to get the oil out of the engine before the ZDP concentration gets so low that it is ineffective at being at the right place at the right time and preventing engine wear so that becomes the long term limit on oil life for that application.

The other things that determine oil life such a acid build up, oxidation, petane insuluables such as silicon from dust/dirt, carbon or soot build up from the EGR in blowby, water contamination, fuel contamination, etc.... are all modeled by the multipliers or deterioration factors that "adjust" the immediate slope of the line defined by the engine revolution counter as those items can be modeled in other ways and accounted for in the immediate slope of the ZDP depletion line.

The algorithm was developed over the course of many years by several lubrication experts at GM Fuels and Lubes, spearheaded by Doctor Shirley Schwartz who holds the patents (with GM) for the algorithm and the oil life montitor. I had the luck of working directly with Dr. Schwartz when the idea of the oil life monitor first progressed from the theoretical/lab stage to real world testing/development/validation. There were fleets of cars operated under all conditions that deteriorate the oil life for any and every reason and , thru oil sampling and detailed analysis of the oil condition, the algorithm was developed, fine tuned and validated to be the most accurate way invented yet to recommend an oil change interval by. As just one example, I have seen cars driven side-by-side on trips, one towing a trailer and one not, for instance, to prove the effectiveness of the oil life monitor in deteriorating the oil at a faster rate just because of the higher load, higher average RPM, higher temps, etc...and it works flawlessly.

The oil life monitor is so effective because: it is customized for that specific vehicle/engine, it takes everything into account that deteriorates the oil, it is ALWAYS working so as to take into account THAT INDIVIDUALS driving schedule, and it tailors the oil change to that schedule and predicts, on an ongoing basis, the oil life remaining so that that specific individual can plan an oil change accordingly. No other system can do this that effectively.

One thing is that I know personally from years of testing and thousands of oil analysis that the oil life algorithm works. There is simply no argument to the contrary. If you don't believe me, fine, but, trust me, it works. It is accurate because it has been calibrated for each specific engine it is installed on and there is considerable testing and validation of the oil life monitor on that specific application. NOt something that oil companies or Amsoil do. They generalize....the oil life monitor is very specific for that application.

Oil condition sensors in some BMW and Mercedes products are useful, also. They have their limitations, though, as they can be blind to some contaminates and can, themselves, be contaminated by certain markers or constituents of certain engine oils. Oil condition sensors can only react to the specific oil at that moment and they add complexity, cost and another potential item to fail. One other beauty of the GM oil life monitor is that it is all software and does not add any mechanical complexity, mass, wiring or potential failure mechanism.

There is considerable safety factor in the GM oil life monitor. Typically, I would say, there is a 2:1 safety factor in the slope of the ZDP depletion curve....in other words, zero percent oil life per the ZDP depletion is not zero ZDP but twice the concentration of ZDP considered critical for THAT engine to operate under all conditions reliably with no wear. This is always a subject of discussion as to just how low do you want the ZDP to get before the oil is "worn out" if this is the deciding factor for oil life. We would tend to be on the conservative side. If the oil life is counting down on a slope that would recommend a 10K change interval then there is probably 20K oil life before the ZDP is catostrophically depleted....not that you would want to go there...but reason why many people are successful in running those change intervals.

Please...NOT ALL ENGINES ARE THE SAME. The example above is an excellent practical justification of why you would want to add EOS and change the 15W40 Delvac in the muscle car at 3000 miles max and yet can run the Northstar to 12500 easily on conventional oil. You must treat each engine and situation differently and what applies to one does not retroactively apply to others. This is where Amsoil falls short in my book by proposing long change intervals in most everything if you use their oil. It just doesn't work that way. You can run the Amsoil to 12500 with no concerns whatsoever in the late model Northstar because even the oil life monitor tells you that for conventional oil off the shelf. Would I do that to the 502 in my 66 Chevelle...NO WAY. Amsoil says I can though. Wrong.


There are entire SAE papers written on the GM oil life monitor and one could write a book on it so it is hard to touch on all aspects of it in a single post. Hopefully we hit the high spots. Realize that a GREAT deal of time, work and energy went into developing the oil life monitor and it has received acclaim from engineering organizations, petroleum organizations, environmental groups all across the board. It is not some widget invented in a week and tacked onto the car.

pogiskier 05-03-2011 11:06 PM

This cool I would like to learn more.

coolman 05-03-2011 11:17 PM

So I guess me waiting until I get the warning is the right thing to do. I always say, Why waste the oil when there's nothing wrong with it. I usually get about 6 to 7 thousand miles on my trucks before I need to change according to the monitor. That saves a lot of money and down time when you have a fleet over taking them in every 3,000 miles weather they need it or not.

TOMS1SS 05-04-2011 12:08 AM

:clap:Let's just hope that 3,000 miles or less BS has been put to rest for good.

Milk 1027 05-04-2011 12:10 AM

Just changed mine with 10% left.
Seems like the right time to do it.

TOMS1SS 05-04-2011 12:14 AM

Quote:

Originally Posted by Milk 1027 (Post 3177898)
Just changed mine with 10% left.
Seems like the right time to do it.

Just changed my oil in both my cars:

Camaro: 7,200 miles with 28% left after one year. The manual says to wait for the DIC or one year.

Fiesta: 10,076 miles when the oil change sensor went off. The Ford manual states to change the oil every 10,000 miles.

- For the record many car companies go a lot further than even 10,000 miles. Oil is SOOOOO much better than was when 10W40 and 3,000 miles were the standard.

MARINE1991 05-04-2011 12:22 AM

yea I am waiting to it goes to about 10% before I take it in... synthatic last longer and protects better then reg oil.. :happyanim: I must admit, did not think it was that involved, just thought it went by GM and the Mileage since the last oil change... :iono:

lawman007 05-04-2011 12:31 AM

I like it when research vilifies my laziness...lol!!!:facepalm: That was good that GM did provide the research in developing this feature.
Troy Lawson

TJ91 05-04-2011 12:36 AM

very helpful, thanks for the post. I change mine at 30% oil life yet, not neccessary but theres piece of mind for me, as going lower does not harm the engine. However, is there a TSB or something on GM reseting the oil life monitors on our Camaros? I swear I heard something like that, not sure if it was a rumor or not. None the less great thread!

Lumix 05-04-2011 01:19 AM

Quote:

Originally Posted by TJ91 (Post 3177937)
However, is there a TSB or something on GM reseting the oil life monitors on our Camaros? I swear I heard something like that, not sure if it was a rumor or not.

I heard the same thing. Don't have a clue if it's true or not. Wish there was a reliable way to find out.

Number 3 05-04-2011 05:29 AM

I've posted often that there is a ton of science behind the OLM on GM vehicles. There is still a lot of skepticism based on the "old school" and personal history.

I still go to get the oil changed in Mrs. Number 3's Malibu. She has 100 mile highway commute and the OLM will easily go to 10,000 miles. I always get the, "ohhhhhhhh, you shouldn't wait so long to get the oil changed, it's verrrrrry dirty". So someone less technical or without the belief in the science might be scared back into the 3,000 mile change.

GM never really got the credit for this, but their point was to be greener by changing your oil as needed, not at 3,000 miles "just because".

Mark H 05-04-2011 06:05 AM

Quote:

Originally Posted by Number 3 (Post 3178133)
I always get the, "ohhhhhhhh, you shouldn't wait so long to get the oil changed, it's verrrrrry dirty". So someone less technical or without the belief in the science might be scared back into the 3,000 mile change..

Do you ever tell them who you are and where you work?
Could be pretty funny.
Mark

kennyo 05-04-2011 06:22 AM

Very informative.That's what I looked at it as-a widget.Definitely gonna wait til 10% now.

Sir Nuke 05-04-2011 06:27 AM

Quote:

Originally Posted by TJ91 (Post 3177937)
very helpful, thanks for the post. I change mine at 30% oil life yet, not neccessary but theres piece of mind for me, as going lower does not harm the engine. However, is there a TSB or something on GM reseting the oil life monitors on our Camaros? I swear I heard something like that, not sure if it was a rumor or not. None the less great thread!

Quote:

Originally Posted by Lumix (Post 3178010)
I heard the same thing. Don't have a clue if it's true or not. Wish there was a reliable way to find out.

There IS something, but it has to do with the same V6's in Caddy's (same engine in our Camaros). I have one, and I got the notice in the mail about a month ago. It was labled as a RECALL but all it said was, and I ask my service manager about the specifics, they (GM/CADDY) recalibrated the system, no parts were changed. The deal is, in the Caddy's, there have been reported timing chain failures and/or advanced wear based on the oil change frequencies based on the monitor system alone. SOOOO it was time for me to get the oil changed anyway, had the dealer do the oil/filter change and do the update to the monitoring system while they were at it.

Seeing as how I have typically done all my oil changes at the 50% mark, which was normally at or about the 10000 mile mark or aq little more.....I figure I was more than safe.

Ironheadspearo 05-04-2011 06:42 AM

I have been running mobile 1 synthetic extended mileage oil for the past 5 years now, it is rated up to 15,000 miles. the problem with this is that oil filters are not matched up to go the 15,000 miles. in the past i was buying the best filter i could get and running them upwards of 13000 miles with no issue. i would feel the oil and inspect it when drained and even with 13000 hwy miles on it the oil felt actually pretty thick like new oil would just black. at 7000 miles it was still semi translucent. I now run the oil to 13000 in the camaro but with a top mounted filter it is easy to change out the filter every 4 or 5 thousand miles. the main thing when running your cars mileage up vetween oil changes it to every 2 to 3000 check the level because you will need to add some most likely. adding some new to replenish the old that was lost also helps freshen up the oil some. you will save a ton of money doing it this way especially if your on the hwy alot. i used to change it every 3000 with regular oil but for me it was every month i was changing oil.

Russell James 05-04-2011 06:52 AM

I got the same recall notice for an Acadia w/ 3.6 L I use to own. It was to reprogram the Oil Life Monitor due to premature timing chain failures.

That tells me two things. The timing chains aren't so great. And, those real long oil change intervals may not be so great if they can contribute to an engine problem.

I never bought into the OLM theory, 3 -5 K changes for me. I've done a ton of oil changes on other peoples cars where they take it down to 0% on the OLM, and that oil looks nasty. I'll trust my eyes before theories, and now there is a recall to back up that suspicion that real long oil change intervals may not be so great - gee who'd of thunk it.

fielderLS3 05-04-2011 07:01 AM

Another problem with these long oil change intervals is that most people never check their oil. How many engines have been ruined by people assuming everything is fine because of the monitor running their cars out of oil.

I'd never use the oil life monitor. I go by how it looks on the stick. I know using the oil monitor is "probably" ok, but "probably" doesn't cut it when it comes to an engine on a $35,000 car.

shawn18 05-04-2011 07:06 AM

I check mine regularly and change it around 35-40%

Markel 05-04-2011 07:14 AM

Thank you for posting this! :w00t:

camaro1 05-04-2011 07:16 AM

its good in theory,, but it just doesnt work,, especially when people use cheap oil,, and no one checks their oil anymore, then people complain that they have their low oil light come on but they have 8000 miles on their oil change.

gm is re-programming many of the v6 engine ecm's to make the oil change light come on sooner because of all the problems these engines are having with oil issues

scottyvegas 05-04-2011 07:22 AM

Great info..

TooCool5 05-04-2011 09:34 AM

Quote:

Originally Posted by Fearer2010SS (Post 3177905)
Just changed my oil in both my cars:

Camaro: 7,200 miles with 28% left after one year. The manual says to wait for the DIC or one year.

Fiesta: 10,076 miles when the oil change sensor went off. The Ford manual states to change the oil every 10,000 miles.

- For the record many car companies go a lot further than even 10,000 miles. Oil is SOOOOO much better than was when 10W40 and 3,000 miles were the standard.

Looks like I will be going to the one year interval too. My Mobil1 oil has 5,200 miles on it and 40% Oil Life. in 10 months.

CamaroSpike23 05-04-2011 09:54 AM

Quote:

Originally Posted by fielderLS3 (Post 3178235)
I'd never use the oil life monitor. I go by how it looks on the stick. I know using the oil monitor is "probably" ok, but "probably" doesn't cut it when it comes to an engine on a $35,000 car.

so you'd rather trust your eyes (that I'm sure are calibrated to judge actual contamination of oil, not just its "dirty look") over a system designed by engineers for the sole purpose of telling you if your oil is good or not?

sorry, but "How it looks on the stick" doesnt cut it when it comes to an engine on a $35,000 car.

Quote:

Originally Posted by camaro1 (Post 3178271)
its good in theory,, but it just doesnt work,, especially when people use cheap oil,, and no one checks their oil anymore, then people complain that they have their low oil light come on but they have 8000 miles on their oil change.

gm is re-programming many of the v6 engine ecm's to make the oil change light come on sooner because of all the problems these engines are having with oil issues

define cheap oil.

you talking regular dino oil vs synthetic? the system works with both types of oil.

el ess A 05-04-2011 10:06 AM

OnStar is "on my butt" about the Camaro OLM reading like in the 80s yet it's been a bit over a year since an oil change.

Quote:

Your vehicle is due for required maintenance because your oil life system has not been reset for 12 months.
Hence the little warning sign on my OnStar report. They suspect I'm not resetting my OLM, but fugg 'em. Car only has 6800 miles on it. So when I change my oil, THEN I'll reset it.

I've used the OLM to schedule oil changes for all the vehicles so equipped and never had an issue with any of them. None. I believe...

IROCanSS 05-04-2011 10:07 AM

I can't remember the last time I changed my oil. Checked it yesterday... Full, pretty clean and 51% on the indicator. I think I changed it last fall... :iono:


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