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Thank you for the very informative post on the GM OLM. Finally the inside scoop that could never be duplicated in an article.
ZDP depletion and GM oil life monitor
- Thread starter bbobynski
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I think what he was getting at is that they take a generic one-size-fits-all conventional as the LCD so that the oil monitor is always 'safe', and then they derate the oil monitor so that when it says 'zero life', it still has some saftey built in.
Sounds good if you want to run conventional oil I guess.
It would be nice if you could program it for your paticular brand, so if you put M1 5W-30 EP it would adjust the curve to take it into account.
Well BB, thanks for finally coming over, I hope you enjoy the visit. I lost my modem for a week and missed all the fun! I told you it would be a good time though. Looks like you've been very busy considering the number of posts you've put out, thanks for the effort. Anyway, about the only person we haven't heard from yet is JohnBrowning, but he should be driving up in his Toyota anytime now. I must apologize for the way the original thread (comments from a GM engineer)degraded into an attack on GM, it was embarrasing for me to even read it. Sorry.
I would appreciate it if you replied to Mike on that original thread about the piston slap issue in GM trucks. The effort here over the last several years has been to "solve" the "problem" with engine oil/viscosity selection...some avid readers would feel much better about their vehicles if they were told the truth on how and why this situation occurs. I think you have done a great service to GM by explaining the OLM, and the country in general. Thanks again. I probably should stick one of those flashing signs here.......
I would appreciate it if you replied to Mike on that original thread about the piston slap issue in GM trucks. The effort here over the last several years has been to "solve" the "problem" with engine oil/viscosity selection...some avid readers would feel much better about their vehicles if they were told the truth on how and why this situation occurs. I think you have done a great service to GM by explaining the OLM, and the country in general. Thanks again. I probably should stick one of those flashing signs here.......
Pablo...
I don't understand your first question. The oil sample data that GM used to develop the oil life monitor does show that the ZDP depletion occurs at a fairly linear rate based on cumulative engine revolutions. If you look at the raw data of ZDP concentration vs. cumulative engine revolutions there is obviously quite a bit of scatter but with enough engines tested and enough oil samples a clear pattern emerges and it makes perfect engineering sense based on how ZDP works. The algorithm is based on best fit assumptions of a linear correlation to the ZDP depletions with plenty of safety factor.
The oil life monitor starts at an assumed concentration of ZDP in the oil that is based on the low end of the GF4 specs. So, there is even more safety factor built into the computation.'
Certainly, using oil with more anti-wear additive will add more safety factor to the oil life calculation. If the ZDP depletion is the long term reason controlling the oil life depletion to zero, then the higher fortified oil will simply add more safety margin to the oil life change interval.
Where this gets sticky and hard to re-calculate based on any given oil is that the greater deterioration factors for acid buildup, contamination, oxidation, etc...could be the reason for the change interval counting down to zero oil life. Simply changing the ZDP concentration in the calibration would throw off the calculation for the other factors that could be one of the determining factors for an oil change, not just the ZDP depletion. The ZDP depletion just serves as the basic model for the other calculations to "pile on" to...
My explaination of the oil life monitor is a very simplistic approach. The oil life monitor is very complex with quite a bit of proprietary software code in it to accurately model the different functions that affect oil life. There are "books" written on the system that are internal to GM so describing it completely in an internet post is impossible. The fundamentals are outlined but there is a lot of specific modeling in the system to make it accurate.
Certainly using better oils will only add more safety factor to an engine following the oil life monitor for changes. Given that it is impossible to predict which of the factors that will trip the monitor in any given customers hands it is equally impossible to predict exactly how much (if any in some cases) the "better" oil might improve the oil life past the monitor prediction.
I don't understand your first question. The oil sample data that GM used to develop the oil life monitor does show that the ZDP depletion occurs at a fairly linear rate based on cumulative engine revolutions. If you look at the raw data of ZDP concentration vs. cumulative engine revolutions there is obviously quite a bit of scatter but with enough engines tested and enough oil samples a clear pattern emerges and it makes perfect engineering sense based on how ZDP works. The algorithm is based on best fit assumptions of a linear correlation to the ZDP depletions with plenty of safety factor.
The oil life monitor starts at an assumed concentration of ZDP in the oil that is based on the low end of the GF4 specs. So, there is even more safety factor built into the computation.'
Certainly, using oil with more anti-wear additive will add more safety factor to the oil life calculation. If the ZDP depletion is the long term reason controlling the oil life depletion to zero, then the higher fortified oil will simply add more safety margin to the oil life change interval.
Where this gets sticky and hard to re-calculate based on any given oil is that the greater deterioration factors for acid buildup, contamination, oxidation, etc...could be the reason for the change interval counting down to zero oil life. Simply changing the ZDP concentration in the calibration would throw off the calculation for the other factors that could be one of the determining factors for an oil change, not just the ZDP depletion. The ZDP depletion just serves as the basic model for the other calculations to "pile on" to...
My explaination of the oil life monitor is a very simplistic approach. The oil life monitor is very complex with quite a bit of proprietary software code in it to accurately model the different functions that affect oil life. There are "books" written on the system that are internal to GM so describing it completely in an internet post is impossible. The fundamentals are outlined but there is a lot of specific modeling in the system to make it accurate.
Certainly using better oils will only add more safety factor to an engine following the oil life monitor for changes. Given that it is impossible to predict which of the factors that will trip the monitor in any given customers hands it is equally impossible to predict exactly how much (if any in some cases) the "better" oil might improve the oil life past the monitor prediction.
BB, thank you for a great post. I think educating the consumer is a thankless but very important task by business. To me, oil life monitors are the future, no if and or buts. Another amazing miracle made possible by micro-electronics.
Probably a validation of imitation being the sincerest form of flattery is that Honda is going with these as well.
How does GM see 5W-20 oil in its future?
Probably a validation of imitation being the sincerest form of flattery is that Honda is going with these as well.
Educating the customer is hard but so is educating the dealer. I have had discussion with several service managers, salesmen and techs. I live in a small area and happen to know both GM dealers and some of the pople who work there from my 35 yrs of doing business with them.
GM needs to put more pressure on the dealers to stop psuhing 3000 miles oil changes on customers to rake in more service profit. A elderly relative was looking a getting a new Buick. She asked me about taking care of the car and to help her decide on what to buy. I happened to mention about the OLM )amoung other things the new cars had) and no need to change oil till the light comes on. She buys a new Rendevous and the salesman tells her not to rely on that oil change light and still change the oil every 3 months or 3000 miles. Naturally she beleives him and not me or even the owners manual.
[ April 20, 2005, 09:02 AM: Message edited by: Mike ]
GM needs to put more pressure on the dealers to stop psuhing 3000 miles oil changes on customers to rake in more service profit. A elderly relative was looking a getting a new Buick. She asked me about taking care of the car and to help her decide on what to buy. I happened to mention about the OLM )amoung other things the new cars had) and no need to change oil till the light comes on. She buys a new Rendevous and the salesman tells her not to rely on that oil change light and still change the oil every 3 months or 3000 miles. Naturally she beleives him and not me or even the owners manual.
[ April 20, 2005, 09:02 AM: Message edited by: Mike ]
I bought a new Cadillac last July and after about 2 1/2 months got a letter from the dealer saying I need to bring it in for 3,000 mile service. The OLM was showing over 60% remaining life with close to 3,000 miles on the odometer. Anyway, I decided it wouldn't hurt to have the oil changed post break-in to be safe. Of course, the dealer put a window sticker reminder on to bring it in after another 3 months or 3,000 miles. It has now been close to 6 months and I've gotten a letter from the dealer that I'm overdue for serivce, and this week got a letter from GM that I'm overdue for my 9,000 mile service (7,000 on odometer). Of course, I know they are estimating milage, but I'm disappointed how hard they are pushing to ignore the OLM.
The good news is when I drove in for the first service, my salesman greeted me in the waiting room with a coupon for a free oil change, and the letter I received from the dealer a few weeks ago included another free oil change coupon. Guess I should shut up and quit complaining.
Boy, isn't that the TRUTH. Back in '96 when I purchased a Cadillac STS I knew far more about the vehicle and it's options than did the salesperson, and he was one of the rare salespeople who had been with the same dealer selling Cadillacs for over 10 years.
The typical level of product knowledge from the customer facing people in most automobile dealerships is horribly low. Not one in ten deserves to call themselves a professional.
The service department is all about generating revenue, not about providing the best service and advice. Hence 3,000 mile oil change reminders, the addition of all kinds of expensive and useless engine additives and the gross overselling of extra work.
Really ticks me off
John
Don't know. How did they manage to design/develop/validate the intakes and intake gaskets on most V6 and vortec V8's that have been leaking coolant internally for 10yrs?
bbob, my wife 1994 STS has an OLM, but she thinks it's just a simple 3K counter with possibly a time limit. Is this true? When did the real deal OLM come into being? Or is she simply wrong? 7.5 qt. sump and easy enough driving, I tend to believe her.
I think that is why my very good GM dealer service manager is skeptical of the OLM as the gospel. It absolutely works, but you must have a good fitting air filter and no coolant leak issues to get there. The OLM assumes a properly working system, but it sometimes isn't.
The OLM is a good tool, but doesn't make it a no brainer until some of these other issues get resolved.
The "real deal" GM oil life monitor works as I have described it in the post above.....that is the way it has always worked since it's inception in the early 80's and first application in production in the 1986 model year. There has never been any sort of oil life monitor that is simply a mileage counter on a GM car so your wife is wrong....good luck convencing her, though...LOL.... The oil life monitor field validation work actually was done on Cadillac 4.5 and 4.9 engines back in the mid-80's when the algorithm was being validated and fine tuned for production. There was extensive testing of the oil life algorithm (working as I described in the treatise above...) on the Northstar engine before it ever went into production and I can assure you, positively, that the oil life monitor in a 94 STS is NOT a simple mileage counter and that it works exactly as I have described it...I know this personally for a fact...so you can show this to your wife...LOL.
The designers are working under constraints that the owner may not care so much about. They have fuel economy targets, noise levels and other items that could be less important to the owner and therefore, a change in viscosity could be warranted.
Case in point. My Focus came with 5w-20. Earlier (MY 2000) came with 5w-30. I called Ford Racing and, based on their experience in Zetec Midgets and Formula Ford Zetec, they recommend a 40wt oil while I am on track. Obviously, my priorities are not the same as those that the original designers take into account when specifying 5w-20.
If you extend your logic, then one would never modify ones car in anyway. The factory determined that 205 width tires are best, so changing to 215s would be wrong. The factory determined that the original engine calibration was best, so programming my own on a dyno (SCT) would be wrong.
I agree that the designers might have a level of knowledge that is hard to beat. However, that does not mean that they are infallible or that the owner cannot successfully tailor the viscosity of the oil to their own particular habits and needs.
Is this contrary to Patman's theory that GC 0W-30 is the best oil for the vette' in terms of absolute wear #'s? And the M1 0W-40 is better theory?quote:
Originally posted by buster:
Do you have any info on how GM tested Mobil 1 in the Corvette? I read somwhere that they ran the car around a track and very high speed until the gas tank was low. They then tore down the engine and mearured wear. Also, what are your thoughts on oil analysis and engine wear? Is that something GM does when evaluating an oil?
I do agree with you in that many engines today don't need high levels of anti-wear additives. Another area where BITOG UOA's show this. Toyota must really be doing something right.
No, I was making a point. If the logic that the factory knows best for oil viscosity is true, it could be true in other cases. That is not putting words in your mouth, as I did not indicate that those were your feelings.
What about the case of technological advances? Car comes from the factory filled with 10w-30 and that is what recommended, but technology allows a 0w-30 to do all the 10w-30 ever did and more. Then what? Is the factory still right?
What about the case where a factory has a contract with an oil company to use their oil and they do not make a certain weight of oil and, therefore, it cannot be recommended? As with the above example, what if another manufacturer can supply an oil that will do what the recommended weight does and more?
You presume that the factory always has in mind EXACTLY the same goals as the owner. This is simply wrong. You are correct that it is always a good choice and more often than not, it is easier to make a mistake by changing than it is to make an improvement. However, to imply that the factory recommendation is always the best for an unmodified vehicle, seems to me to be a little pretentious when coming from a factory engineer. There is a chance that an owner could want something different from their car (and oil) than the multitude of constraints that were placed upon engineers at the time of development.
It appears to me that both of you are in agreement, so it escapes me as to why the continued posting. You are happy in doing your own "testing", and he is happy that you are happy in doing your own testing.......
yep, just ran it around the track a time or two and called it good.....LOL LOL LOL ..... I think you have the aftermarket mixed up with the OEM's. That is how they do it....quote:
Originally posted by buster:
Do you have any info on how GM tested Mobil 1 in the Corvette? I read somwhere that they ran the car around a track and very high speed until the gas tank was low. They then tore down the engine and mearured wear. Also, what are your thoughts on oil analysis and engine wear? Is that something GM does when evaluating an oil?
I do agree with you in that many engines today don't need high levels of anti-wear additives. Another area where BITOG UOA's show this. Toyota must really be doing something right.
What you read was completely wrong.
Any engine program like the LS1 for the Corvette, the LS6 currently and the upcoming LS7 are testing on dyno and in cars for YEARS before release to the consumer with the specified lubricants and coolants and such.
In the case of the Mobil 1 in the Corvette I would hazard a guess that the number of dyno engines run with Mobil 1 is in the hundreds....like somewhere between 200 and 300 all total. These are engines that run for 200, 300 , 400 or more hours at full throttle, max RPM, max power and are then torn down and analyzed in a variety of ways for wear and other lubrication performance. This is on top of the countless specific bench and dyno tests run on the specific lubrication system, cold start lube system performance, cold overpressurizaration (start at -20 and go immediately to 5000 RPM), cold start field testing and driveability, engine cooling testing, etc. Fleets or test cars are running with the production intent designs and lubes on accelerated durability, endurance, emissions, track testing, etc... The products are testing far in excess of what any customer can do.
In the case of the Northstar engines that spec Mobil 1, the Mobil 1 was part of the test program for those engines from the very beginning so every test and dyno engine that ran used Mobil 1. Similarily, the Supercharged Northstar for the upcoming STS-V/XLR-V has used Mobil 1 throughout the test program so it is a well proven entity. Plus, yes, it was run "around the track" a time or two....LOL.
Just to confirm, GM is NOT changing from DexCool or to another formulation of coolant or anything. DexCool is the factory fill coolant and will be for the forseeable future. There are no plans nor development program to change from DexCool. None. Period...rumors to the contrary are simply....rumors...with no truth in them.
Some of the rumors may have started due to GM approving different suppliers of the DexCool. Texaco was the original supplier, having developed the product with GM and Shell was also an approved source. Prestone is currently approved (their "long life", "universal" coolant is basically the DexCool formulation in a different color) as well as Valvoline is now approved to supply DexCool. But...it is still DexCool and will be DexCool.....
sooo....teamDFL....let me be more specific.... What I was referring to was your statement "If you extend your logic, then one would never modify ones car in anyway. The factory determined that 205 width tires are best, so changing to 215s would be wrong. The factory determined that the original engine calibration was best, so programming my own on a dyno (SCT) would be wrong."
I am not saying this nor promoting this type of logic at all.
I maintain that the factory setup is the best set of parts that meet all the requirements for the car. If you are willing to put up with more tire noise, less fuel economy, greater wear, etc....then put whatever tires on the car you want. I have no problem with that as long as you take the responsibility for the changes and understand that there was logic and reasoning behind the original selection from the OEM. Too many times people want to pile onto the OEM's for cheaping out or doing things that they consider stupid when they have no understanding whatsoever of what the requirements were or how the part had to perform.
My answer to the question was simply that of the best, proven product for the car in question. Not a "what-if" for down the road changes.
I have no problem with personalizing any vehicle to the owners requirements or expectations....I do get just a little defensive when people imply that I think it is "wrong" to change something from what the factory said as you implied above.
I find that most people, when they take the time to ask the question of "why did the factory do it that way" are often surprised at the reasons and most often agree that the OEM choice was correct given the requirements (many of which they had no idea of)
Until you have the resources to run as many dyno engines on test as the OEM's do you have nothing but speculation to back up your claims of other grades of oil performing as well or better than the factory recommended grade. My point is that the stuff recommended (as are all OEM parts) is PROVEN. Anything else is not. It might work for you and it might seem OK but until the product works thru the complete range of customer requirements and is tested on a multiple of trials it is still a guess as to it's performance.
In this vein, it was interesting recently on one of the Cadillac forums where the new STS was being discussed. On the same page of discussions topics there were posts berating the performance of the tires on the car on the race track. Other posts berating the wear rate. Other posts berating the car for not performing in the snow.... Seems like we got the tires about right...LOL....they seem to **** off everyone... In all seriousness, this is a perfect example of what we are talking about. The tires are an obvious compromise for a lot of things and seem to work well for about 90 percent of the owners. The others might find a "better" choice..but the snow tires one selects are going to be poor track tires for the other.
I often read posts where people claim to "eliminate the compromise" in the factory design...hmmm....when asked what they did they usually describe a modification that actually compromised the system FAR more on some respects than it was in the OEM configuration. Guess it is just your definition of compromise.
BTW....we will use whatever weight of oil or whatever product we want in the engine. It has nothing to do with a "contract" with a particular company or anything like that. The engine development guides what the engine or program needs. Often, a new engine or program will define what a new lube or coolant or ???? is, instead of the other way around. It is ludicrous to think that an OEM would be locked into using some inferior product due to the limitations of any given supplier. There are too many other suppliers out there willing to do exactly what you want.
I am not saying this nor promoting this type of logic at all.
I maintain that the factory setup is the best set of parts that meet all the requirements for the car. If you are willing to put up with more tire noise, less fuel economy, greater wear, etc....then put whatever tires on the car you want. I have no problem with that as long as you take the responsibility for the changes and understand that there was logic and reasoning behind the original selection from the OEM. Too many times people want to pile onto the OEM's for cheaping out or doing things that they consider stupid when they have no understanding whatsoever of what the requirements were or how the part had to perform.
My answer to the question was simply that of the best, proven product for the car in question. Not a "what-if" for down the road changes.
I have no problem with personalizing any vehicle to the owners requirements or expectations....I do get just a little defensive when people imply that I think it is "wrong" to change something from what the factory said as you implied above.
I find that most people, when they take the time to ask the question of "why did the factory do it that way" are often surprised at the reasons and most often agree that the OEM choice was correct given the requirements (many of which they had no idea of)
Until you have the resources to run as many dyno engines on test as the OEM's do you have nothing but speculation to back up your claims of other grades of oil performing as well or better than the factory recommended grade. My point is that the stuff recommended (as are all OEM parts) is PROVEN. Anything else is not. It might work for you and it might seem OK but until the product works thru the complete range of customer requirements and is tested on a multiple of trials it is still a guess as to it's performance.
In this vein, it was interesting recently on one of the Cadillac forums where the new STS was being discussed. On the same page of discussions topics there were posts berating the performance of the tires on the car on the race track. Other posts berating the wear rate. Other posts berating the car for not performing in the snow.... Seems like we got the tires about right...LOL....they seem to **** off everyone... In all seriousness, this is a perfect example of what we are talking about. The tires are an obvious compromise for a lot of things and seem to work well for about 90 percent of the owners. The others might find a "better" choice..but the snow tires one selects are going to be poor track tires for the other.
I often read posts where people claim to "eliminate the compromise" in the factory design...hmmm....when asked what they did they usually describe a modification that actually compromised the system FAR more on some respects than it was in the OEM configuration. Guess it is just your definition of compromise.
BTW....we will use whatever weight of oil or whatever product we want in the engine. It has nothing to do with a "contract" with a particular company or anything like that. The engine development guides what the engine or program needs. Often, a new engine or program will define what a new lube or coolant or ???? is, instead of the other way around. It is ludicrous to think that an OEM would be locked into using some inferior product due to the limitations of any given supplier. There are too many other suppliers out there willing to do exactly what you want.
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