Oil Life System - For Real?

[MILVET]

Got a 2005 Silverado Crew LT 5.3l. Read in owner's manual that it has an oil life monitoring system that displays the Oil-Life Percentage left in the Drivers info center. The manual states that the oil doesn't need to be changed until 0%. Supposedly the computer monitors and factors in miles driven, engin temps and rpms to get the Life % left. I bought my truck used in 10/05 with 4.3K miles and the Oil life was 100% after dealer oil change. I now have 11.4K and the Oil Life is at 45%. Should I continue to trust this or should I change the oil regularly regardless? Should it be every 3 or 5k miles? Which oil is best 5w30 or 10w30 and regular, synthetic or blend?
Thanks in Advance!!!

TEL

[silveradoHO]

I still change mine every 3000 miles. According to the manual it's not necessary, but I figure no more than it cost, it's cheap insurance.

[TexasF355F1]

If you go with synthetic I would change every 3500-5000. Regular oil, every 3000.

[jethro_3]

Read this and make your own decision. Oil Life

If we all continue to change the oil at 3000 miles and do not believe that oil has gotten better than the dinosour oil from your grandfathers life, I want to thank you for wasting oil........

Sorry........

[JCL82]

I'm going throw this out there. So i just pass my 2nd year of using amsoil. I change it once year or 20,000 miles and change the filter every 6 months or 10,000 miles. Sooo after two years i have 100,000 miles on the truck and the engine is still doing good. I'm getting 18-20 mpg depending on how i drive for the week. Now i just change the oil and going on to the 3rd year. Here's to a good 3rd year.

I'm not trying to say go buy amsoil, i'm just saving alot of time and money. Sure up front it cost alot to buy the oil,but i'm saving in the end.

[Ape0r]

I use M1 and dump it at 6-7k, whenever I get around to it. I'm confident that it could go longer, but it just pains me to leave it in there for so long =).

At my last change I forgot to reset the OLM, and it took a total of about 9300 miles to run down enough to give me the change oil message, including about 350 miles of towing a ~2500 lb trailer and a LOT of highway driving.

You've got to figure out what you're comfortable with. 3k mile oil changes are a thing of the past, I'm considering pushing it to 8k, pretty impressed with JCL82's intervals, though =).

So, each 6k I spend $25 on oil and (6000 miles)/(19 miles/gal)*($3/gal) = $947 on gas.. ouch.. I'm gonna go cry now..

[guumbah]

Is it just me, or did the 3000 mile limit come to our group consciousness along with the quickie-change places like Jiffy Lube and such? They pound it into our heads with endless commercials, print ads, etc. I'm just as guilty, changing my own around 3000 every time, but I doubt it's REALLY necessary.

I haven't actually read that section of the owner's manual on any of my vehicles in many years, but I distinctly remember my first couple of cars' manuals saying anywhere from 5000 to 8000 depending on the manufacturer. I know growing up my dad never did his more often than 5000. He regularly got 100,000+ out of cars.

Think of it like those almond commercials where the growers ask us all to eat a can a week...

[MT-2500]

Originally Posted by MILVET

Got a 2005 Silverado Crew LT 5.3l. Read in owner's manual that it has an oil life monitoring system that displays the Oil-Life Percentage left in the Drivers info center. The manual states that the oil doesn't need to be changed until 0%. Supposedly the computer monitors and factors in miles driven, engin temps and rpms to get the Life % left. I bought my truck used in 10/05 with 4.3K miles and the Oil life was 100% after dealer oil change. I now have 11.4K and the Oil Life is at 45%. Should I continue to trust this or should I change the oil regularly regardless? Should it be every 3 or 5k miles? Which oil is best 5w30 or 10w30 and regular, synthetic or blend?
Thanks in Advance!!!

TEL

I think that one is a little off or telling a little white lie..
Always go by the mileage on your odmeter.
Check your owners manual on oil wt.
All of the better brands of oil is good.
Synthetic has a better lube quality in cold weather and real hot weaher or severe driving.
And will last more miles. But just like regular oil it gets dirty or the dirt in the oil is the main wear factor.
A good reason for good filter and to keep it changed.
MT

[MILVET]

Thanks for the info. I guess I have to get past the "Quickie" propaganda that has been drilled into my head and go with cold hard facts (Ref Bob's Article). Truth is I asked because I've asked 5 different "Experts" and received 5 different and sometimes totally contradictory answers. I agerage 16-17 mpg in town and 18-21mpg on the road. I've noticed in the past that my average mpg drops by .5mpg each 1K miles after 4k miles. This was true for my 2000 Chevy and still true for my current one. I think I'll base my personal decision to change oil on mpg since I think gas prices will go up faster than my oil will deteriorate. Thanks again for the awesome response!

TEL

[guumbah]

Originally Posted by MILVET

I think I'll base my personal decision to change oil on mpg since I think gas prices will go up faster than my oil will deteriorate.

Seriously! It can't be cost effective to worry about a couple of extra oil changes/year vs an extra $3+ per mile past a certain distance. For what I pay for one tank of gas I can change my oil at least 3 times.

[wrparks]

I too don't trust the oil life monitor very well. I once intentionally did not reset it after an oil change and drove another 5000 miles and it still did not say to change it. Thats 10,000 miles and no oil change?

Admittedly, I don't jam down on the accelerator and rarely go over 2200 rpms even when accelerating, but I can't make myself go that long and trust the monitor. Do we need to change it at 3000, not most of us, only if you drive in the desert with 40 mph winds kicking up dust. Or, if your commute takes 1 hour to go 10 miles.


My wifes saturn monitor kicks in at about 6000 miles and all she does is interstate driving at ~70. Personally, a 5 or 6000 mile interval is sufficient unless using synthetic (which I don't so I can't say what I'd do there). My old 4.3 blazer went 245,000 miles and never had the oil changed before 5500 miles or so. Still ran (poorly) when I sold it so obviously the oil change interval didn't hurt too much.

The monitor is good for those who don't want to keep up with it and need a reminder. And I'm probably wrong not trusting it because I'm sure it has been validated, but I just can't do 10,000 miles. Besides, now I only go about 10,000 miles a year on my truck and change it every 6 months just to keep the condensation out.

[guumbah]

Originally Posted by wrparks

Besides, now I only go about 10,000 miles a year on my truck and change it every 6 months just to keep the condensation out.

Ditto here. My commute is early morning, so it only takes 10 minutes to go 10 miles, and I barely approach 12000 miles a year. My wife's car is even less. Last year she did under 5000 on her <1 mile commute that she walks at least half the time (love the part-time driver discount on our insurance ). And do the math, both vehicles are more than 50% non-commute driving (=mostly not stop & go). Mine pretty much ends up being 3 times/yr, hers twice.

[SLJ2137694]

I copied the following from another forum. If you don't believe in the "Oil Life System" after reading this I'm afraid you are hopelessly stuck in old technology thinking!


"I used to be a die hard 3000 mile oil change guy, but now I go by the oil life monitor and I'm very confident it works.

The following is from Bob is the Oil Guy forum, one of the developers of the system wrote this nice write up:
http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=1;t=010523;p=0

Pasted here for your convenience.

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

BTW....something I forgot to mention. The oil life monitor was developed, validated and works fine with conventional oil...yes, non-sythetic, conventional, off the shelf SG4 gasoline engine oil.

I have seen the results and they are fine. Anyone that indicates that the oil life monitor is not designed for conventional oil is wrong. Synthetic oil is NOT required if you plan on following the oil life monitor.....which you should."