Skip to main content

Read our primer articles on High Mileage Oil, Synthetic Oil and Kinematic Viscosity

Some thoughts on GM's OLM

Icon 1 posted Profile for bbobynski Email bbobynski Send New Private Message Edit/Delete Post Reply With 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.

The oil life monitor is not under the control of a summer intern at GM Powertrain per an earlier post....LOL Not that a summer intern wasn't compiling calibrations or doing a project on it but is under control of the lube group with a variety of engineers directly responsible that have immediate responsibility for the different engine families and engine groups. The idea that a summer intern was responsible for or handling the oil life monitor is ludicrous.....LOL LOL LOL
More...

The OLM does NOT just monitor engine revolutions. Each specific engine has a stored maximum "bank" of set engine duty cycles (revolutions) between OCIs, reset by the user at time of service. Each time the PCM fires, it subtracts the number of revolutions from the bank. When the bank = 0, the "Change Engine Oil" or oil light illuminates. Outside air temp, coolant temp, cold soak time, throttle load, vehicle speed, etc. are all accounted for in an effort to predict oil temperature, which in turn assess an exponential penalty factor. If the oil temp is above or below the standard algorithm allowance, the amount of degradation increases and is subtracted from the bank value at a higher rate. Hence, if you drive short trips in cold temps, the OLM ticks away faster. If you track your Vette with high rpm/loads, the OLM ticks away faster. If you tow, well you get the idea...

The ONLY thing the OLM cannot account for is a mechanical engine fault. If you have a leaky air filter or a coolant leak, the OLM will never know or change it's signaled OCI. This is where and oil condition monitor would be superior. GM chose this route for simplicity/cost. They are willing to stake a 5yr/100K powertrain warranty on it, so it can't be too terrible.

IMHO, the intervals are a bit on the high side, usually signaling for a change right at the time the oil is spent. I prefer a buffer of 10-20%, but have no qualms about going to 0%. I have yet to see a bad UOA by following the OLM
quote:
Originally posted by Captain Kirk:
quote:
Originally posted by Trajan:
I'm not interested in what "dealers" are saying. I want the link to what mfgs are saying.

I also want the proof that car makers are pushing for what you claim.

I certainly haven't received any notice from a dealer to come in sooner than what the OCI already is.


http://www.asashop.org/autoinc/nov2009/cover.htm


GM 6094M is based on the same specifications as ILSAC GF-4 but additionally includes some specific GM requirements. GM 4718M is the GM high performance oil specification that goes well beyond the industry standard ILSAC GF-4 and API SM specifications. The Mobil 1 grades that carry GM 4718M have been fully approved and tested against GM 4718M. The companion Mobil 1 Extended Performance viscosity grades have not been formally approved against GM 4718M but will provide the performance at GM 4718M level. Engine testing required to get formal approval is limited to certain Mobil 1 products only.

This is for European cars including those imported to America:

http://www.techmax.ca/european...l_specifications.htm

This one comes from shell

http://www.motoroilmatters.org...Shell%20-%202009.pdf

This one talks about the politics behind the scenes in Europe and the U.S.
http://www.smartmotorist.com/c...-specifications.html

Pretty straight forward!!





Ummm, neither addresses what you claimed. Remember, Cadillac reducing the OCI?

The first in the series of non answers concerns the difference between API cert and ACEA.

You really should read it, as it does not support your "arguement" about bad oil.

I use ACEA cert oil. I don't care if it is API cert. If it isn't ACEA A3/B3, it doesn't go into my engine. I've made that clear on many occasions. ACEA isn't new you know.

The second concerns the use of low quality oil AKA non API/ACEA/Whatever certed. Like a certain oil we all know.

Still waiting for the proof for the CTS claim.

The overriding thing is that this thread is about a mower engine that uses mineral oil, and doesn't sludge.

The owner attributes that to a good engine design and use of certified oil and regular changes. The owner is also quite aware of what causes sludge.
In a motor vehicle having a direct or an indirect injection engine containing lubricating oil which has a useful life that varies in accordance with engine operating conditions, a method for advising the operator of the vehicle of the need to change oil, such method comprising the steps of:

Periodically calculating an effective engine revolutions value over predetermined intervals during a present engine operation in accordance with a product of measured engine revolutions and engine oil temperature and engine oil contaminant penalty factors which operate to increase the effective engine revolutions value to compensate for engine operating conditions that tend to cause increased degradation of the engine oil, the oil temperature and oil contaminant penalty factors being determined as a function of engine oil temperature and engine oil contaminant values, respectively;

Decreasing a stored remaining allowed revolutions value indicative of the remaining number of engine revolutions allowed for the useful life of the engine oil by subtracting the calculated effective engine revolutions value; and

Actuating an indicator advising the operator that the engine oil needs to be changed when the stored remaining allowed revolutions value falls below a predetermined threshold value indicative of the end of the useful life of the engine oil.

2. A method as in claim 1 further comprising the step of calculating the engine oil temperature value in accordance with engine parameters prior to calculating the effective engine revolutions value.

3. A method as in claim 1 further comprising the step of determining the engine oil temperature value by measuring an engine oil temperature from an engine oil temperature sensor prior to calculating the effective engine revolutions value.

4. A method as in claim 1 further comprising the step of calculating the engine oil contaminant value in accordance with an oil temperature value, fuel injection timing, fuel quantity and engine rotational speed prior to calculating the effective engine revolutions value.

5. A method as in claim 2 wherein the step of calculating the engine oil temperature value includes the steps of:



When the engine oil temperature value is in a warm up range, calculating the oil temperature in accordance with a measured initial coolant temperature at the beginning of a current engine operation and a sum of engine revolutions since the beginning of the current engine operation; and

When the engine oil temperature value is in an equilibrium range, calculating the oil temperature in accordance with a measured coolant temperature, engine rotational speed, fuel quantity, intake air temperature and vehicle speed.

6. A method as in claim 2 wherein the step of calculating the engine oil temperature value includes the steps of:

When the engine oil temperature value is in a warm up range, calculating the oil temperature in accordance with a warm up equation T.sub.o =T.sub.ic +k.sub.1 R.sub.e wherein T.sub.ic is an initial coolant temperature at the beginning of a current engine operation, R.sub.e is sum of the engine revolutions since the beginning of the current engine operation and k.sub.1 is a constant; and

When the engine oil temperature value is within an equilibrium range, calculating the oil temperature in accordance with an equilibrium equation T.sub.o =k.sub.2 +k.sub.3 S.sub.e +k.sub.4 T.sub.c +k.sub.5 F.sub.q -k.sub.6 T.sub.a.+-.k.sub.7 V.sub.s wherein S.sub.e is engine rotational speed, T.sub.c is a coolant temperature, F.sub.q is fuel quantity, T.sub.a is an air intake temperature, V.sub.s is vehicle speed, and k.sub.2, k.sub.3, k.sub.4, k.sub.5, k.sub.6 and k.sub.7 are constants.

7. A method as in claim 4 wherein the step of calculating the engine oil contaminant value includes the steps of:

calculating the engine oil contaminant value, C, from an equation
C=k.sub.8 +k.sub.9 I.sub.t +k.sub.10 F.sub.q +k.sub.11 T.sub.o +T.sub.o +k.sub.12 S.sub.e,
wherein I.sub.t is fuel injection timing, F.sub.q is fuel quantity, T.sub.o is the calculated oil temperature value, S.sub.e is engine rotational speed, and k.sub.8, k.sub.9, k.sub.10, k.sub.11 and k.sub.12 are constants.
quote:
Originally posted by snakedoctor:
If the was a problem with Cadiliac engines, there would be a techanical service bulletin on it. I have not seen one. Is there one. you tell us???


TSB.....give it time........

I did not had any engine trouble on the 2005 I had, but my friend did. His engine went out at 30,000 miles. He bought it used and it had the certified 100,000 mile warranty. I am wondering, too, if Cadillac has a problem with their engines. I rolled into the dealership with my 2009 CTS with 8,000 miles for the first oil change. I talked to the service advisor and he said that they were now recommending 6,000 mile oil changes; they were having problems with some of the engines at 50,000 miles. He said not to go by the monitor. My monitor would have let me go at least 10,000 miles.

I am certainly not saying that I let my maintenance go. I, too, check the oil on a regular basis. That is just common sense if you want to make an engine last. When I had my 2005 CTS, I went to the Cadillac dealership to get the oil changed at 5,000 miles. He told me that was not necessary because it was synthetic, and that I needed to go by the monitor. I asked the dealership on the last oil change if they were still going by that recommendation. At 8,000 miles, mine was at 40% and I just did not want to go any further. He told me that they, the Cadillac dealership, were now recommending 6,000 miles because what they had found was that, if you went by the monitor and the number of miles it allows, they were beginning to have engine problems at around 50,000 miles on some of the 08's and 09's. They attributed this to people changing their oil in the 8,000 to 10,000 miles range.
quote:
Originally posted by snakedoctor:
Golly, they sound so smart


They are smart.......and so are these guys

The Japanese Automotive Standards Organization (JASO) has created their own set of performance and quality standards for petrol engines of Japanese origin.

By the early 1990s, many of the European original equipment manufacturer (OEM) car manufacturers felt that the direction of the American API oil standards was not compatible with the needs of a motor oil to be used in their motors. As a result many leading European motor manufacturers created and developed their own "OEM" oil standards.

ACEA YOU SAY!

Because of the real or perceived need for motor oils with unique qualities, many modern European cars will demand a specific OEM-only oil standard. As a result, they may make no reference at all to API standards, nor SAE viscosity grades. They may also make no primary reference to the ACEA standards, with the exception of being able to use a "lesser" ACEA grade oil for "emergency top-up", though this usually has strict limits, often up to a maximum of ½ a litre of non-OEM oil.
How in the heck did this topic go from me showing a half-way decently maintained lawn mower engine to crap about Garbage Caddy's? Cadillacs have gone downhill since the 1980's. All they are now are re-badged Chevy's and GMC's, with a power ashtray and phony walnut trim and made in Canada (not the United States).

My post was about proving Engine Design has a lot to do with sludge. The Geeks at B&S design these little engines for abuse. The tolerances are loose, the oil galleries are as big as the Lincoln Tunnel, and they are simple. These little engines are designed to see severe service, that no vehicle engine will ever see, unless you convert you caddy to a lawnmower.

I do buy American, Yes, my Titan has a Nissan badge on it, but it was built in Canton, MS. The engine was built in TN. I don't care for anything built by UAW, and their 10 minutes work, 20 minutes break, 45 an hour to bolt wheels on the lugs, then have 3 Union meetings to get more $$$ for doing a crummy job.

Dave
quote:
Originally posted by Deltona_Dave:

I don't care for anything built by UAW, and their 10 minutes work, 20 minutes break, 45 an hour to bolt wheels on the lugs, then have 3 Union meetings to get more $$$ for doing a crummy job.

Dave


Big Grin Wasn't that bad when I was in the UAW. But our plant had nothing to do with autos. Scott Paper was out biggest customer.
quote:
My post was about proving Engine Design has a lot to do with sludge. The Geeks at B&S design these little engines for abuse. The tolerances are loose, the oil galleries are as big as the Lincoln Tunnel, and they are simple. These little engines are designed to see severe service, that no vehicle engine will ever see, unless you convert you caddy to a lawnmower.


This should clear up the small engine question

Just thought I should add that small engines don't have high tech sophisticated emission systems like cars do... further stressing the oil. Car engines are also plagued with short trips,incomplete warm ups,condensation and so forth that all contribute to oil oxidation. Small engines will run hot and burn off VOC'S ,condenstation,and fuel intrusion. There exists no possible coolant intrusion into the oil in those small air cooled engines to boot.

The small air cooled engines do run the oil to higher temperatures compared to water cooled engines which can pose another set of possible issues in some cases!!
quote:
Cadillacs have gone downhill since the 1980's. All they are now are re-badged Chevy's and GMC's, with a power ashtray and phony walnut trim and made in Canada (not the United



You might want to re-consider you Cadillac assertions and read this Dave. Most foreign car buyers like yourself trash American cars......yet have not owned American ever......or maybe over 30 years ago.

So how could you even know about American cars....let alone trash them??

A high tech Cadillac engine should be running the same kind of oil that Vettes run...........preferably group IV/V oil would be my choice. High tech engine gets high tech oil...Period!! Many will be rolling off the line with the good stuff already in the crankcase if not already!!!

http://en.wikipedia.org/wiki/Cadillac_CTS
Last edited by captainkirk
Post
×
×
×
×
Link copied to your clipboard.
×