Do you really trust the oil life indicator?

[Mr Monte]

My son was replacing cams almost every week on LS motors that the owners changed oil only based on the oil life gauge & probably never checked their oil level.

I change oil/filter every 6-9 months or when I can feel some drag in the throttle response. What I've notice is my OHC engines need an oil change by 3,000 miles but my OHV engines can go 6,000 miles without any issues.

[ChocoTaco369]

Originally Posted by =Stephens=

So I am at 35% remaining life, which is more that 3000 miles. And I am going to change my oil today. What do you change yours at? This has probably been posted about before but there are new members who might not have seen a post like this or don't want to go searching for it.

Let me ask you this: do you trust the mileage rule for oil changes?

Let's explore the 3,000 mile oil change theory. Do you agree that all types of driving: aggressive driving versus conservative driving and highway versus city driving are all equal? Let's Guy #1 lives in a city and drives hard stoplight to stoplight and Guy #2 babies his car on a highway commute daily cruising at 65 mph. Both guys change their oil at 3,000 miles. You're in the market for a used car and both guys are selling them for the same price, same year, same make and model, same color. Which would you rather buy?

Lots of things impact the life of the oil. Driving style, commute type, climate and air quality all play a role. Some engineer slaved away trying to take these environmental factors into account. Is the OLM completely accurate? Probably not, but I'm willing to bet it's surely more accurate than the blanket "6 month/3,000 mile" rule regardless of environment and driving style. I'll be following the OLM's recommendations.

[IMPERIALBLUE2SS]

No I don't trust it, never have. I change my oil every 5k on all my vehicles with Mobil 1 synthetic. Usually ends up being every 7-8 months. I have a log book for every vehicle and write down everything that's done mileage, date, and staple receipts to the pages. Got a 1 truck, 3 cars, and 2 motorcycles. Too much to try to remember with all theses vehicles.

[Abomb1223]

I use the oil life indicator . . and it usually comes to just above 5k

[kevint]

Originally Posted by ChocoTaco369

Lots of things impact the life of the oil. Driving style, commute type, climate and air quality all play a role. Some engineer slaved away trying to take these environmental factors into account. Is the OLM completely accurate? Probably not, but I'm willing to bet it's surely more accurate than the blanket "6 month/3,000 mile" rule regardless of environment and driving style. I'll be following the OLM's recommendations.

This. OEMs are surprisingly good at employing smart engineers.

[NYJets77]

I thought I read on Camaro5 someplace a while back that the oil life monitor is based only on mileage since last change, and nothing more sophisticated.

If that's still true, its not very scientific.

[2011*Camaro*SS]

I change mine when the OLM gets to 5-10%. Thats what my dealer recommends and thats also what they do with my moms Escalade and dads Benz. I don't drive much so I should change every year. I've changed my oil twice and owned the car just under 3 years. Its has 14,500 on it this morning.

[Sp00ner]

Originally Posted by NYJets77

I thought I read on Camaro5 someplace a while back that the oil life monitor is based only on mileage since last change, and nothing more sophisticated.

If that's still true, its not very scientific.

That is horrendously inaccurate...

[ChocoTaco369]

Originally Posted by Sp00ner

That is horrendously inaccurate...

As are most beliefs on a car forum. Everyone wants new technology, but no one trusts it. Old dog, new tricks, something something is how it goes, right? People still put 160 degree thermostats in their car for power increases because they believe truisms from 1967 exist in 2014.

Change your oil at 6 months/5,000 miles and one of two things will happen:

1.) You're throwing money away because it still has life left in it.

2.) You're changing it too late because you're rough on your vehicle for various personal or environmental factors.

Synthetic oil is rated for what, up to 15,000 miles these days? You have a 1-in-15,000 chance that 5,000 miles is the time to change your oil. You have a nice, fancy new car with all kinds of sensors and gauges telling you what to do. GM has raised their powertrain warranties from 3 year/36,000 miles to 5 year/100,000 miles. It would be a pretty lousy business model if they over doubled their engine warranty and simultaneously cut the accuracy of their maintenance tools. That'll lead to quite a few major warranty claims.

[SPARTAN sui]

To add, here's how it really works, quoted from this thread

http://www.camaro5.com/forums/showthread.php?t=145143

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.

[jrpimp00]

Too much, I heard, I thought, my friend said, etc; in this thread. But there is no way you can determine an oils viscosity breakdown just by the way it looks. Oil can look black/dirty within 10 miles of driving. LOL

[Jrichards73]

Got a ford e-150 with 160k and 5 oil changes, runs like a top....

[motorhead]

I own a fleet of work trucks the are changed only off the OLM, and I have been doing this since GM has been using them. I never had any motor problems on one truck ,out of many over the years, that had anything to do with internal wear. That's good enough for me to know it works. I can only imagine all the money in oil changes and lost production time I've saved over the years by not changing according to mileage. You old schoolers keep waisting your time and money. Maybe one day you'll realize that you're not driving your Daddies Chevy or using his oil anymore.

[=Stephens=]

Thanks for all the good advice, I guess it is cheaper to buy oil than to replace parts in the engine. I drive mine everyday and have 60,000 miles on mine now. Still runs like a champ. Mobil 1 full synthetic since my first oil change.