Oil Life Index/Monitor (OLI/OLM) mileage

[thu]

I have 10,000 miles since the last oil change. The OLI/OLM says I have 32% oil life left. That means the oil will have about 14,700 miles on it when the OLI gets down to 0%. My driving consists of about 95% highway (80+ MPH).

How many miles have others been getting from their OLI and what is the mix of driving that you do?

[JimD]

With my '04, the driving mix is around 70% city and I am changing oil at ~~ 11,000 miles and that is with taking the OLM down to 0%. I cannot find the thread, but I believe the guru mentioned a maximum interval of 12,500 was built into the OLM for 2000+ engines.

With a pre-2000 engine and less than 50% city miles, I am averaging 6,800 miles between changes.

[BodybyFisher]

Jim, this is from the GURU, here is the reference to the 12,500 in late model NS's, Mike

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

[Cadillac Jim]

I noticed early-on that my oil life indicator read 50% when I had put in 3,000 miles of city driving. Although I use synthetic oil, I change when the oil life indicator shows 50%. When my engine was pulled down at 116,651 miles, it looked like a new engine under the cam covers. We didn't pull the pan or heads; we sent the core back to Jasper. Maybe I'm pampering my baby, but so what? It's my baby.

[Cadillac Jim]

Jim, this is from the GURU, ...

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

I have some experience with interns and new hires. Really good interns that exhibit ability to work without supervision, awareness of ambience, and a demonstrated sensitivity to all stakeholders in a project as well as requirements, cost, practicality, and schedule, are allowed to function as essentially full team members; this is extraordinary and very, very rare. New hires – not summer interns – that show the same capabilities and promise are allowed REA (responsible engineering authority) responsibilities in their first year or two to speed their development, but are never allowed to sign off approvals themselves.

GM has world class capabilities among the car people. I was at Hughes Aircraft Company when they were a division of GM, and one of the first things that they did was an intercultural exchange of systems engineering, project management, risk management, and requirements-driven quality control (remember Six Sigma?). A lot of this came from DoD-driven competitive evaluations and Government requirements, like Carnegie-Mellon software maturity models, IEEE 1200, DoD 5000.2, and ANSI/EIA-731/732 and EIA-632, etc. The bottom line is that the GM management capabilities and practice of the car people are world class and second to none.

If you want anecdotal evidence that this is true, look at what happens if you have a computer-based module problem in a high-end BMW or Mercedes vs. a Cadillac or Chevrolet. I heard tales in the 2003 time frame that repairs of computer-related problems of a high-end BMW could take 90 days because the dealer was helpless and those problems went back to Germany, where they didn't have the car at hand to work with. We solve those problems here for others with the car sight unseen, I know, but the really difficult ones go to the dealer and their full-bore machines with the "real" PCM interface and displays, and the highly trained guys they have for these cases. You will be out the same day, or the next day if they must wait a day for a part to come in from another state, barring transmission overhaul or other multi-day repair. When Mercedes needs to field a really high performance car, they subcontract to AMG to insulate the team from the corporate structure. When GM or Ford needs to do it, they form a team internally. Of course, we remember that Ford found GM's team supporting the Super Sport and Chaparral projects and hired all of them away to kill GM's racing efforts in the 1960's and fielded the GT-40, but... I digress.

We all know that GM has management issues. These are not the car design, development, manufacturing, and support people, who are a tiny percentage of GM. These are the guys at the top who report to the Board of Directors and are selected by them, again a tiny proportion. Since they are stock-price driven, their business horizon is 90 days or their next expected job slot date, whichever is nearer (pardon a little irony here). This results in things like emphasis of high-profit models and definition of design points for fielded models that are based on computer-based estimates of what will maximize profits, not what will be the best deal for the consumer, a very well-known loser philosophy that disregards the memory and insults the intelligence of the buying public.

The car people brought us the Northstar, the Corvette, the CTS, the XLR, the V-series, the Honda MSX, the Mercedes AMG series, the BMW M series, etc. The Boardroom brought us the Escalade and the Ford Excursion and listed the highway tire pressure for the Explorer at 28 psi for a better ride and then blamed Firestone for tire failures. The car people take these oversized SUVs forced on them by the marketplace and the boardroom and try to make them safe and drivable; note the Ford Escape Hybrid and the GM performance hybrid program. Pardon me if I exaggerate a little to make a point.

This is true of all car companies to one extent or another. GM was worst at bean-counter management in the 1980 time frame and they are still improving communication between business and car people. They have a long way to go to get to where Toyota and Honda are, in my opinion, but they understand the problem and are working it.

[JimD]

Dino 10W-30 oil changed per OLM at 0% (average 6,800 miles)

No additives

Picture at 148,xxx miles

That is assembly line paint on the intake cam.

http://i70.photobucket.com/albums/i101/Jim...mbearingcap.jpg

[JasonA]

Thanks Jim. I tried taking a picture of mine the other day. Same story, conventional 10W-30 oil, changed per OLM, 153k miles. The casting of the head is still 100% aluminum-colored silver. Not a single SPECK of any sludge or even discoloring. It's actually very impressive. But my camera isn't as good as yours and the photo was blurry.

[thu]

So, are you guys saying that even though the extraplolated mileage the OLM says I'll get is close to 15,000 miles, it will tell me to change the oil at 12,500 anyways?

Thanks, BodybyFisher, for posting the GURU's take on the OLM.

[KHE]

So, are you guys saying that even though the extraplolated mileage the OLM says I'll get is close to 15,000 miles, it will tell me to change the oil at 12,500 anyways?

Yes - the system is capped at 12,500 miles.

[thu]

Ok. I think I'll change at that time when it tells me to.

Thanks

[JasonA]

Yes - the system is capped at 12,500 miles.

That's for 2000+ engines, is that correct? 1993-1999, it's capped at 7,500 I believe, due to the lack of the roller followers, etc.

[BodybyFisher]

I have more on the OLM, here it is, I was only addressing the 12,500 issue mentioned by JimD this morning, here is EVERYTHING you wanted to know about the OLM, by the GURU... Please understand that this may be confusing as I have copied MANY of his OLM posts from different threads! He is THE MAN...Mike

***************************************************************************

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