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Oil Life Monitor (OLM)


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I was searching around for information on the OLM. I know that guru posted a detailed analysis of it. Does anyone have it saved? I even looked over at cadillacforums but I could not search because I am not a contributing member. I think I have the OLM info from the guru on my server, I will check later.

I found this post. A few of the posters did not believe in the OLM and mechanics and dealers talked it down. By the end of the thread, they were believers.

http://caddyinfo.ipbhost.com/index.php?showtopic=4543&hl=

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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I'm trying to remember what I had to say before my cable modem went out on me here ! It just seems that mine would never even make it to 5k miles and I recall twice that it barely made it to 4k miles. It would never make it to the 7k miles with the mixed driving I do. Maybe Im just to hard on it LOL :o

Per the other post my transmission (TLI)life is located in the dic I wasnt aware the 1996 Deville had one on it that you have to look up with a scanner ? What I was telling you was that its never changed from 100 % upon asking the dealer about this they said they never got an answer from GM and they have asked many times ! From the way SCott the Service Director made it sound theres several Cadillacs running around with this issue.

However Mike thatnk-you for caring enough to educated me :)

Do you ever sleep ? looks like you were up all night yourself ? I was sick anywho and up most of the night.

Michael

http://www.gm.com/company/gmability/enviro...nce_040104.html

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This is one part of several posts I captured over the years. Quoting here ....

I will respectectfully disagree with your first statement for the

reasons I mentioned in my post before. Hours ALONE has no way to

comprehend the driving schedule of the engine. Not that hours isn't

possibly a good indicator under certain

conditions...i.e...industrial equipment that is started and run on a

dedicated, predicable schedule, marine use where the engine is

always working hard, tractors and such where the engine is run at a

very regular load cycle, etc. Personally, I use an hour meter on my

lawn/garden tractor to determine change intervals as the engine

always runs for at least 2 hours when it is started and it is run at

a specific RPM.... Cars, however, have such a varied duty cycle with

varying loads, speeds, run times, cold soaks, hot soaks , etc. that

useing hours alone is a very poor way of determining oil life. It

may work IN YOUR SPECIFIC CASE based on your oil measurements,

etc.....but....it would NOT work for everyone and is a poor

recommendation for recommending oil change intervals for the general

public.

Imagine the grandma or housewife....er...houseperson....that cold

starts in the winter, drives 1 mile to the school, drives 1 mile to

the grocery store, cold soaks for an hour, drives 1 mile

home....etc..... It would take a long time to accumulate your

"hours" yet the oil would need changing much much much sooner than

in my car that runs on the interstate for an hour each time it is

started regardless of the weather. Hours alone just does NOT hack

it.

Remember, GM is responsible for ALL drivers and possible use

schedules for the vehicles we produce and responsible for

recommending the change intervals for oil and fluids to provide the

best possible balance between engine life and environmental issues

and maintenance issues. The first thing that ANYONE working on

maintenance intervals will tell you is that there is NO SINGLE

MAINTENANCE INTERVAL FOR EVERYONE. Period. Miles, hours, days,

etc....just do not hack it. Any comphrehensive maintenance schedule

MUST take into account a myriad of factors beyond simple hours. That

was what drove the initial development of the oil life monitor.

There were Drs. of Chemistry working with the engineers that

developed the system and millions of dollars were spent developing

the correlation for the various reasons requiring an oil change with

a measurable, quantifiable, predictable metric. The oil life monitor

was the result. It was developed, tested, and validated on a myriad

of vehicles on a myriad of driving schedules for the specific

purpose of predicting oil life in the specific vehicle it is

installed in. There is absolutely NO WAY that anyone can provide a

more accurate way of recommending an oil change for that

vehcile....regardless of lab samples, hours recommendations, etc.

I appreciate the experience you have in regard to oil analysis and

such but I would still trust the oil life monitor developed by GM

for that specific vehicle long before I would trust the

recommendations of someone who knows little about the makeup of the

engine or vehcile and recommmends changing oil based on a single

specific parameter. You know that there is much more to changing oil

than hours......I hope.

Interestingly, during our research and development on the oil life

monitor back in the mid 80's and early 90's we tried various labs

around the country for oil sample analysis to backup our facilities

at the GM Research Labs and basically gave up after getting poor

repetition on sample analysis, inaccurate analysis, etc.... We did

all our research on samples in house, finally, to avoid some of the

problems we encountered with outside labs. Not sure of their

ultimate capability but I would personally be reticent to trust my

oil analysis to an outside lab based on my experience.

As stated, if oxidation were the ONLY reason to be changing the oil

then temp and hours might be a good indicator and you might be able

to make the statement that "Since it only gets Mobil1, my oil in

reality probably has over twice that life remaining with the

longevity advantages of synthetics." Oxidation, however is RARELY

the reason the oil needs changing and that is really the ONLY place

that synthetic oil surpasses conventional oil for performance.

Contamination, ZDP depletion, etc. all are much more commonly the

reason for an oil change and synthetic provides ablsolutely NO

ADVANTAGE there. That is why the oil life monitor is basically the

same deterioration for synthetic or conventional oil. In a case like

dirt, dust and metallic contamination (pentane insoluable

contaminants) the synthetic oil has absolutely no advantage and

synthetic does not have any higher "dose" of the ZDP in the oil to

guard against wear. So it really isn't any "better"....it will just

live at higher temps than conventional oil. That is why I personally

use it in my air cooled, backup generator that runs oil temps of 320

on a hot day!!! Good use for synthetic.

The oil life monitor was designed to accurately model oil life.

Period. Not push the limits of the oil or the engine. The decay

rates and degradation factors calibrated for any specific vehicle

are designed to provide an accurate predicition of oil change

intervals for that vehicle with a sufficient safety factor so that

the oil is nowhere near "used up" totally when the oil life

indicated is zero. In fact, to insure that there is adequate safety

factor built into the oil life monitor the durability cars that GM

runs to validate the vehicles on an accelerated mileage accumulation

schedule over a WIDE variety of driving and climatic conditions

usually run 2 TIMES the oil life interval for actual

changes....meaning that the oil is actaully changed every other time

the oil life monitor says to. The oil is sampled at the "first"

change recommendation before resetting the oil life monitor and then

sampled and changed at the second change recommendation. The engines

look perfectly fine at the end of 100k or more on this schedule.

I have seen Northstar engines run in HD livery service in livery

fleets around Detroit and LasVegas that had the oil changed per the

oil life monitor and the engines ran 300K with no problems at

teardown at the end of the schedule. Same for 4.5/4.9 engines that

ran in taxi cabs in Pennsylvania for 250-300K. So the oil life

monitor is accurate and it does NOT minimize engine life.

Understand that if the grandma that "housewifes" the car to death in

the winter never takes any long trips and always cold starts for

short trips, the oil life monitor may tell her to change oil in as

little as 500 miles on very severe duty like that. Simple hours

would never pick up on that.

I , too, have done a considerable amount of development of oil life

and engine performance over the years (32 and counting) and

personnally worked with the development of the oil life

monitor...so...from what I know of it and my experience with it I

would not trust any other form of oil change recommendation.

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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Have been changing oil based on the oil life monitor for 145,000 + miles on my '98. I change the oil at 0% life remaining, not 20% or 10% remaining.

In fact, I have enough faith in the safety factor built into the oil life monitor that I have run close to 1,000 miles after the 0% indication without worrying about it for even one second.

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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Jim,

May I ask does your Seville use any oil ? . Im not trying to disagree I highly doubt in my right mind Gm would put this on there cars and it a be a safety issue. I guess this goes back to how I have always tried to take care of everything likes its my last :( started when I was small. I use to waxx my bicycle..lol I have ran my car a couple of times maybe 2 until the oil comes on. I just feel bad for some reason, but I need to get myself into that.

Michael -

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Mike, old habits die hard. Keep an open mind. There are a LOT of opinions out there of people who are bias for whatever reason. Sometimes I believe they are biased because they are NOT knowledgable or they have listened to an OLE timer that dudn't believe in that dez new fangled digital gadgets, and say, "I believe in the tried and true, change it every 3,000 miles". And folklore becomes fact in someone's mine. I had a boss in 1984 that would NOT read anything that came off of a computer, he was an old timer. He didn't trust it... because he didn't understand it....

Technology has the ability to more accurately analysis your and my driving habits. These OLM's have a lot of R&D and testing (oil analysis) behind them. We will continue to feed this thread with information. I want this thread to be the SOURCE for information on the OLM for the non believers in us. Keep and open mind and keep reading. Mike

Think about this for a moment, when I was your age, I used to change the plugs every 18,000 miles and possibly regap them in between if I was feeling piggyness. Imagine the IDEA that we can leave plugs in for 100,000 miles and TRANNY fluid in till 100,000 miles. When I was a kid we changed tranny fluid every 24,000 miles and the trannies didn't last as long as they do today and external tranny coolers were not common. Lost of cars had Air Conditioning, but when the AC Compressor died, most just cut the belt off and never got it fixed.

Bow your head when you read this, you are reading the guru's words:

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. <<<< does that paragraph get anyone else excited besides me? :lol:

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

YOU CAN RAISE YOUR HEAD NOW :lol:

THE MAN HAS A WAY WITH WORDS! Mike

post-2998-1146667673.jpg

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Very good stuff ! Tell me more about this attachment I didnt see anything on it or did I miss it? phone wont stop ringing :( cant they call someone else :P

Thanky Mike !

Michael -

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What attachment Body by Fisher? That tag use to be on most all GM cars. Here is a story about Albert, Fred and Charles Fisher (Body by Fisher).

http://en.wikipedia.org/wiki/Fisher_Body

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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What attachment Body by Fisher? That tag use to be on most all GM cars. Here is a story about Albert, Fred and Charles Fisher (Body by Fisher).

http://en.wikipedia.org/wiki/Fisher_Body

Come to think of it I remember where I had seen that tag! Moms 1985 Toronado !!!

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Yep

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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I have thought about buying one ! My mom has had many cars since that car she has always claimes it was the best one she ever had. I have always felt that car as it was somewhat heavy saved her life she totaled that car out crossing the state highway. the same day she got the title out of the mail box :o it was a 1985 Navy on navy with the half top. I use to think as a kid it was really prestigus all that wood and stuff in there real up town .... LOL If only I had a clue as to what the future cars may hold ! I seem to think the 2 I cant put just one . Cars that I have owned that were great cars was my 96 Deville and my 1994 Roadmaster ! I have had to Town Cars 93 and 94 I liked them but never felt the same as I do about a Cadillac. I always say that Im going to open a car lot that specailize in use Cadillacs. The front row would be nothing but 96's Devilles. I'm really wanting something newer for a daily driver than my 98 However I cant say its been a bad car but it seems theres always been some issue. The seats I hate them in that car there Very small ! and hard ! I know im bitching about small seats but I have been thinking about getting an ETC and keeping it . Maybe a Fleetwood 94-96 but I dont like the dash so maybe anotherRoadmaster. anyone looking for a very large car that get good gas mpg 94-96 ! But I'm always looking to buy a car.....lol

The Beatles are on ! Mrs. Robison :) why cant music be what it once was ? yes i'm 24....lol

Michael -

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If you had an STS (with timeserts OUCH sorry :lol:), I would talk to you about an equitible swap, my 96 Deville for your 98 STS (plus or minus cash).... You KNOW my Deville is in good shape (knock on wood)......:lol:

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Yes, I know They wouldnt do it they had claimed they had more come back with issues from the timeserts alone :( I have thought about buying my 96 back! it now has 190k miles on it !

Michael :P

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Yes, I know They wouldnt do it they had claimed they had more come back with issues from the timeserts alone :( I have thought about buying my 96 back! it now has 190k miles on it !

Michael :P

The only reason a dealer would have a Timeserted engine come back is if they didn't follow the repair instructions to the letter...The Timesert was developed during the engine validation process to repair thread bolt holes while on a dyno stand during design and development. A Timeserted block (when done properly) is stronger than a block that left the factory. Anyone who disagrees simply does not understand the proper repair procedure - this includes the dealer that did the work on your car.

Case in point, my '97 STS was repaired by an incompetent dealer in North Carolina - the cretins didn't use the drill fixture and installed the Timeserts too deep in the block which resulted in a 40% loss of thread engagement with the head bolts. The inserts broke when the "tech" torqued the head down. When the previous owner began to again expierence overheating, the dealer fed him the same line "the repair doesn't always work..." That is total BS.

Upon disassembly, I discovered that the Timeserts were .200" - .350" too low in the block. When I machined the block for the Bigserts, I could see that the holes machined by the dealer in the first repair were not on center with the holes I machined for the Bigserts. I KNOW mine were done properly as I used the drill fixture with the kit and followed the instructions to the letter. It is impossible to screw up the repair when the drill fixture is used. It was obvious that the cretin who did the first repair freehanded the drilling process because he was too lazy to spend the time to use the drill fixture and bushing....The end result was that the engine was labeled as "unrepairable" by the cretin tech and the reputation of the Northstar engine was compromised in the eyes of the previous owner and probably the idiot who worked on it. The reality was that an incompetent moron was not following the recommended service practice just to cheat the system.

I'm trying to remember what I had to say before my cable modem went out on me here ! It just seems that mine would never even make it to 5k miles and I recall twice that it barely made it to 4k miles. It would never make it to the 7k miles with the mixed driving I do. Maybe Im just to hard on it LOL :o

Per the other post my transmission (TLI)life is located in the dic I wasnt aware the 1996 Deville had one on it that you have to look up with a scanner ? What I was telling you was that its never changed from 100 % upon asking the dealer about this they said they never got an answer from GM and they have asked many times ! From the way SCott the Service Director made it sound theres several Cadillacs running around with this issue.

However Mike thatnk-you for caring enough to educated me :)

Do you ever sleep ? looks like you were up all night yourself ? I was sick anywho and up most of the night.

Michael

http://www.gm.com/company/gmability/enviro...nce_040104.html

I do not see what the problem is....the fact that your oil change interval varies according to the driving habits is exactly how the OLM works.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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Kevin,

Thank you very much for taking the time to giving me that "understanding" should I call it ? Thank-you ! Do you think I will be ok ? or should I *smurf* before the 12k mile warrenty is up ? :( I dont know why but I just knew I would have to have the head gaskets redone in that car. I do feel that the Seville is more problem-matic than the Devilles I have had. Maybe its the fact that its the first model year for that new body then ? Or maybe its the whole thought how the SLS is tuned and set up ? What I am meaning here is that the STS seems to have a better set up ? Just asking ~!

Thank-you again,

Michael-

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I now use the OLM; and got 6500 miles between oil changes! :o I couldn't believe it!! I just decided that after having a new engine put in the car, and talking with everyone and their grandmother :D , I would make the change. Also, with the old engine, I had to add 2 qts. of oil between the 3000 mile oil changes. New engine, never, and over twice the mileage between changes too, using the OLM... Old engine dripped oil from day one, even after a new seal was installed at 50000 miles. New engine, no drips! I guess all said, I'm a believer... :)

Mark

Mark McDermott

79 Deville 84,000

97 Deville 279,000 :yupi3ti:

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I now use the OLM; and got 6500 miles between oil changes! :o I couldn't believe it!! I just decided that after having a new engine put in the car, and talking with everyone and their grandmother :D , I would make the change. Also, with the old engine, I had to add 2 qts. of oil between the 3000 mile oil changes. New engine, never, and over twice the mileage between changes too, using the OLM... Old engine dripped oil from day one, even after a new seal was installed at 50000 miles. New engine, no drips! I guess all said, I'm a believer... :)

Mark

Mark,

Thats awsome ! I just had many seals put in mine. Im very happy with mine!

Michael-

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Very interesting thread about the oil life monitor.

What is a Hot Soak and a Cold Soak?

Thanks!

Scott

1996 El Dorado

2006 STS

2000 Corvette

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They mean exactly what the sound like... Cold Soak is basically the internal temperature of the engine has reached the ambient temperature. Typically this is an issue at temperatures less than 0 degrees fahrenheit where it starts to dramatically alter oils viscosity. Most times when people are talking about this they are referring to a "rapid" reduction in an engines temperature... Extreme cold weather conditions.

Hot Soak is a little more complicated as some engines can actually heat up more after they are turned off since the cooling system is (again on some cars) no longer active. Turbo cars are usually the ones discussed with regard to this subject as the turbo holds a ton of heat energy and they have been known to "cook"... If they are driven hard and not given a chance to spool down before the engine is turned off... Of course this problem is mostly an issue with oil pressure.

But as an engine "over heats" in a Hot Soak condition the tolerances within the engine are minimized, as everything expands, and friction is increased... You have probable experienced this... Try to start a car after a "hard" run on a hot day and you can sometimes hear the starter..."struggle" against the load...common on Chevys.

Both situations are murder on motor oil.

BTW I love my OLM... One less thing to worry about! I wish my wife's Toyota was so equipped.

caddy.jpg

Easin' down the highway in a new Cadillac,

I had a fine fox in front, I had three more in the back

ZZTOP, I'm Bad I'm Nationwide

Greg

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They mean exactly what the sound like... Cold Soak is basically the internal temperature of the engine has reached the ambient temperature. Typically this is an issue at temperatures less than 0 degrees fahrenheit where it starts to dramatically alter oils viscosity. Most times when people are talking about this they are referring to a "rapid" reduction in an engines temperature... Extreme cold weather conditions.

Hot Soak is a little more complicated as some engines can actually heat up more after they are turned off since the cooling system is (again on some cars) no longer active. Turbo cars are usually the ones discussed with regard to this subject as the turbo holds a ton of heat energy and they have been known to "cook"... If they are driven hard and not given a chance to spool down before the engine is turned off... Of course this problem is mostly an issue with oil pressure.

But as an engine "over heats" in a Hot Soak condition the tolerances within the engine are minimized, as everything expands, and friction is increased... You have probable experienced this... Try to start a car after a "hard" run on a hot day and you can sometimes hear the starter..."struggle" against the load...common on Chevys.

Both situations are murder on motor oil.

BTW I love my OLM... One less thing to worry about! I wish my wife's Toyota was so equipped.

All good stuff great question. I didnt know any of this ! :)

Michael -

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