how accurate is the oil life % in the DIC

[911medic]

Originally Posted by Jenner

How often should you do the differential?? Guess I'll check the manual right

Originally Posted by DagoCountyGee

When do you guys change your rear fluid and tranny fluid??

I did my diff at ~30,000 miles. I think the severe service schedule is at 50,000, and the normal schedule is maybe 100,000.

But it's pretty easy to do, and cheap. My diff took a quart of fluid that cost less than $10. If you can change your own oil, you can change your diff fluid, no problem. If you have a LSD, add a little $$ for some friction modifier, but it's still cheap.

As far as the tranny, I don't know. I think for my auto it's 100,000 or 150,000 miles. I'd like to change the fluid to synthetic, but from what I've heard the autos are a real PITA to do this on, at least for a DIY'er. The manuals I believe are much easier.

[911medic]

Originally Posted by BigBlock69RS

Ask yourself this what is the direct financial incentive to any car manufacturer that your car last 10 years, 15 years or even 20 years with few problems?

Maybe so they can advertise that their cars are the "longest lasting" or quote figures of what percentage of their cars from the last 10 or 20 years are "still on the road today"? So they can build a brand reputation for reliability?

[Rocky1974]

I had a 99 Grand AM GT that I bought salvage in 02. It had 69k on it and if the previous owner took care of the engine like they took care of the interior, it'd probably never had the oil changed. I used conventional oil in it and I changed the oil whenever the light came on and sometimes it went 15k before the light came on. I sold it in 2011 with 212k on it. I never once added a single quart of oil to it and it never had any kind of internal engine failure. I still see it on the road almost daily. I'm a believer in GM's Oil Life Monitoring System.

[skuttduck]

Ok let the flaming begin.


I drive a v6 Camaro. It is a daily driver, and it sees snow and salt. I also change the oil once a year or when the DIC tells me to, whichever comes first.

I can't believe I read the owners manual and listen to the word of GM about the oil change intervals.

[Rocky1974]

There's a study somewhere on the internet(You can google it or I can probably find it.) In the study the guy changes the oil in his 02 Z28 LS1 and puts Mobil 1 in it. Every few thousand miles he would drain a sample and send it to a lab for analysis. The lab would do a complete run down on the oil and send him a report. His conclusion was that about 18k was the proper time to do an oil change on a LS engine running synthetic oil. But what was really interesting was that he got higher levels of metal particles in his oil for about 3k after every oil change, then it would settle down to almost no metal particles for the next 15k. His secondary conclusion was that people who change their oil every 3k may actually be doing more harm than good. I've been of the mind for years that anything under 5k is a complete waste and that the people who preach 3k have been watching too many Jiffy Lube commercials.

[not]

Originally Posted by BigBlock69RS

You really missed the point.

I"m saying there is little incentive for Gm to specify in its maintainence regimen for you to go the extra mile to maximize the life of the vehicle. That goes for any manufacturer not only GM. They are in the business of selling cars and parts. Their interests are reflected in the maintainence plan. It's plain economics.

Ask yourself this what is the direct financial incentive to any car manufacturer that your car last 10 years, 15 years or even 20 years with few problems? Compare that to the incentive that the car last the term of the warranty with minimal issues.

That is my point.

I am as jaded as the regular person, but this is bunk, pure BS. Go to any classic auto show and even guys who have a pristine 57 Chevy will tell you how much better a new C5 Camaro is in regards to fit and finish and new fangled things like brembo brakes and suspensions that keep you in the seat when going around a corner, and an air bag when you dont....

Point is, people with cars with 250k miles on them are great advertisements for people looking for a car/truck. I have a 2000 Subaru Outback with 215k miles and I EXPECT it to go to 300k at which time I will have to figure out if I want to put in a new timing belt and tires...

Sure, GM is out to make money, hope they do, as none of us wants to bail them out, AGAIN.... ever wonder why Hyundai gives 10yr/100,000 mi warranty? Because they were such junk when they first came out.......remember the 1989 Hyundai for $5700? It's cost to fix was so astronomical that you couldn't give them away without a 10/100k warranty.

Thank you.

[Avenging Orange]

Never trust your car to tell you what to do. Regardless, the OLM is still mileage based. Best rule of thumb (and Im sure I'll get flamed for saying it), 3-4k for dino oil, 4-5k semi syn and 5-7k for syn. Thats half the problem these days. We rely way too much on technology and not on our own super computer.....the human brain. The best thing auto makers should put in their cars is a CHECK YOUR OIL message that pops up every 7 days.

[Angrybird 12]

Originally Posted by Avenging Orange

Never trust your car to tell you what to do. Regardless, the OLM is still mileage based. Best rule of thumb (and Im sure I'll get flamed for saying it), 3-4k for dino oil, 4-5k semi syn and 5-7k for syn. Thats half the problem these days. We rely way too much on technology and not on our own super computer.....the human brain. The best thing auto makers should put in their cars is a CHECK YOUR OIL message that pops up every 7 days.

You need to read up on the oil life monitor, it's not just based on mileage. A lot if research and development went into this. It is better than just relying on the old 3-4k schedule.
http://www.edmunds.com/car-care/oil-...g-systems.html
You should check your oil level at every fill up, but that has 0 to do with oil life, Nobody can just look at their oil and tell if it needs changed. Unless it has a viscosity of cold maple syrup or lumps in it.

[Sp00ner]

Originally Posted by Avenging Orange

We rely way too much on technology and not on our own super computer.....the human brain.

I like your viewpoint, and would like to subscribe to your newspaper or periodical. Can you please give me the precise formula that you process each time you get in the car to determine remaining oil life?

Thanks!

[RyanMatthewMiller]

Originally Posted by 2xSSRS

I do it around the 5 to 6%. Get as many miles as I can out of it. It's expensive to change, as you know.

definitely gets pricey.. usually about 110-120 $.. i usually wait until around 20% or so maybe a little lower

[skibik]

First off if the oil monitor on these are based on mileage then why are some saying over 10k miles before theirs were coming on or still at 25% life at over 8k miles and last spring my oil life at 3% at just over 5k miles. It is based on more than just mileage.

Years ago when conventional oil was a buck a quart I believed in 2k miles between changes. Then oil went to a couple bucks a quart then I went 3k. Last car used conventional and at over $3 a quart I went close to 5k or oil change monitor whichever came first. Now with this one I am using full synthetic and I figured 7500 or oil life monitor whichever came first.

I also seen another thread where the poster had his synthetic oil tested after 8k, or whatever was listed, and was told to go for over 10k and have it tested again.

It seems like some of these posts have strayed from what the OP asked. So to the OP you just have to figure out how you want to handle the oil change situation. How often you change is totally up to you. The oil life system these days are way ahead of the ones from 15 years ago. I myself trust it and I am going by it. Usually it is recommended that oil be changed at least once every 12 months. Do what you think needs to be done.

Dean.

[Jenner]

Originally Posted by skibik

First off if the oil monitor on these are based on mileage then why are some saying over 10k miles before theirs were coming on or still at 25% life at over 8k miles and last spring my oil life at 3% at just over 5k miles. It is based on more than just mileage.

Years ago when conventional oil was a buck a quart I believed in 2k miles between changes. Then oil went to a couple bucks a quart then I went 3k. Last car used conventional and at over $3 a quart I went close to 5k or oil change monitor whichever came first. Now with this one I am using full synthetic and I figured 7500 or oil life monitor whichever came first.

I also seen another thread where the poster had his synthetic oil tested after 8k, or whatever was listed, and was told to go for over 10k and have it tested again.

It seems like some of these posts have strayed from what the OP asked. So to the OP you just have to figure out how you want to handle the oil change situation. How often you change is totally up to you. The oil life system these days are way ahead of the ones from 15 years ago. I myself trust it and I am going by it. Usually it is recommended that oil be changed at least once every 12 months. Do what you think needs to be done.

Dean.

I don't mind haha.. I'm learning

[Rocky1974]

From www.bobistheoilguy.com

A Look at GM's Oil Life Monitoring System

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.

[Avenging Orange]

Originally Posted by Angrybird 12

You need to read up on the oil life monitor, it's not just based on mileage. A lot if research and development went into this. It is better than just relying on the old 3-4k schedule.
http://www.edmunds.com/car-care/oil-...g-systems.html
You should check your oil level at every fill up, but that has 0 to do with oil life, Nobody can just look at their oil and tell if it needs changed. Unless it has a viscosity of cold maple syrup or lumps in it.

Ah, but checking your oil has everything to do with oil life. If you have 0 oil in the pan, then the OLM is worthless. Read up on that.

Originally Posted by Sp00ner

I like your viewpoint, and would like to subscribe to your newspaper or periodical. Can you please give me the precise formula that you process each time you get in the car to determine remaining oil life?



Thanks!

Sure thing. Every time I get in the car, I look at the reminder in the upper left hand corner of the windshield