Algorithm for oil service light?

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263
Location
tx
Curious if anybody has ever come across or otherwise decoded the algorithm of a given car for it's oil change service light that newer cars often have these days? I've seen posts on some forums for certain cars that complain that the light just comes on at 'X' miles regardless of driving styles. Yes for the most part the manufacturers claim that things like temperature, usage, RPMs etc are all taken into account. One would reasonably expect that if you go around romping at WOT from every stoplight the light would come on noticeably sooner and if you putter around on the highway cruising at 70 in mild weather it might extend the interval a bit. In theory I'd think they could pretty much account for everything except dusty operating conditions (and even that could be done if there was some sort of air filter monitor... hmmm) This is probably not a simple or realistic answer - just curious what people think or know on this subject. -T
 
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191
Location
KY
Depends on the manufacturer. I think the new Mercedes actually have a sensor that measures the dielectric constant of the oil and extrapolates a value for the oil's usefulness. Honda's lights come on at a specific mileage interval, generally 7500-10000 miles. GM uses an algorithm with a fixed number of "points," with extra points deducted for cold starts or high temperature operation. BMW measures the amount of fuel used. The service light for my Volvo says it will come on after 12 months, 7500 miles, or 750 hours of engine operation, whichever comes first, so it is mostly based on mileage (not many people would run the engine 750 hours or 12 months without putting 7500 miles on the car). One could create an extremely complex model for service intervals, but doing all the possible test cases would be a nightmare, not to mention that different engines have different oil needs, hence, a single model would only be useful for all very similar engines. Interesting note: both my lawn tractor and GMC Sierra have restriction gauges on the air filter box that indicate when an air filter change is required. The one on the tractor is exactly like this one: http://www.dieselpage.com/epc.htm
 
Messages
485
Location
Montgomery, AL
quote:
Originally posted by MolaKule: Why would anyone believe a sensor not based on oil quality/oil analysis?
The automakers are coming up with these predictive models and estimating when the oil will wear out...As does the odometer. I'm with you you MolaKule. A yearly analysis would not guess at your oil's performance, it would show the facts.
 

pgtr

Thread starter
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263
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tx
Thanks Seg, that's just the info I was curious about. Since I have a computer background the GM 'points' algorithm was the most natural to me but I liked the simple elegance of the BMW fuel model too. The dialectric sensor I've seen mentioned before - sounds intriguing. Molakule, keep in mind the world has managed to rack up billions of miles w/ a simple odometer and calender to keep track of various fluids/changes. Not knocking oil analysis but neither do I see a compelling reason for myself or the majority of the motoring public to avail themselves of this service.
 

MolaKule

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Iowegia - USA
I am not knocking computer technology, since I use it every day to analyze thermodynamics, simulate molecular structures, etc. But a computer algorithm is only as good as the programmer and the data programmed into it. With so many variables, it is tough to predict the condition of the engine and its oil. The capacitive or dielectric sensor can be fooled by levels of contaminants. If all the oils could be tested and characterized along with engine wear rates for the many engine and driving conditions, then maybe predictive analysis has some validity, but oil analysis not only shows oil condition but engine condition as well, something the algorithms cannot do today. BTW, I met Sherly Shwartz, the inventor of the oil sensor at a lubrication meeting one time. She also made a presentation and stressed that the oil sensor was simply a first step at a predictive tool, not the final answer.
 
Messages
485
Location
Montgomery, AL
quote:
Originally posted by pgtr: Molakule, keep in mind the world has managed to rack up billions of miles w/ a simple odometer and calender to keep track of various fluids/changes. Not knocking oil analysis but neither do I see a compelling reason for myself or the majority of the motoring public to avail themselves of this service.
You probably don't own a camry. It's known for sludge problems even when following manufacturer's oil change recommendations based on the odometer. If you change at 3K then yes you will not need oil analysis but you will be throwing away good oil.
 

pgtr

Thread starter
Messages
263
Location
tx
You're absolutely right. The billions of miles that were accumulated by cars using nothing but simplistic odometers or even invalid oil service lights was a mere statistical anomaly. Oil analysis is the only safe way to go for all of us.
 

pgtr

Thread starter
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263
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tx
Yes, jjbula, that exception certainly proves the rule that we must all analyze our oils. I'll certainly submit myself to oil analysis reform school [No no] since Camry had a sludging problem.
 
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874
Location
Pacific NW
quote:
Originally posted by pgtr: Yes, jjbula, that exception certainly proves the rule that we must all analyze our oils. I'll certainly submit myself to oil analysis reform school [No no] since Camry had a sludging problem.
pgtr, I don't think anyone is saying the statistic-based lights don't tell anything useful, just that they're only part of the picture. As far as I'm concerned, a light pointing me to my place on a statistical curve is just pointing me to the proper column on the service duty schedule. Light/Heavy/Commercial, etc. That's much better than nothing, but over time, the more exceptions occur with my vehicles, the less accurate the statistics become. They treat oil as a black-box instead of measuring its characteristics. The newer an engine design the worse this declining accuracy becomes. If you're interested in excellence, pushing boundaries, it's up to you to pick an accurate and affordable system of gathering enough data to get the best results. This is true of any scientifically based improvement attempt. With oil, what's enough data? Many of us are still learning. Lights are good. Not complete, but good. IMO, an analysis every few changes would confirm what's really happening, for minimal added cost. On the other hand, an analysis every change for a recent passenger-car engine has to go in the neurotic/learning/hobbyist category. [Smile] Pick your poison. Obviously, huge numbers of the population get along by changing their oil at common denominator intervals. Huge numbers of the population also get along for many years eating at McDonalds. I don't think we're interested in average lubrication or we wouldn't be here, no? David
 

Patman

Staff member
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Oakville, Ontario
Even if the oil change lights aren't 100% accurate, the one good thing about them is that they pull people away from the 3k oil change cycle. When I had the oil life percentage display on my 97 Grand Prix GTP, I noticed that by the time I got to the 5000 mile mark, and was about to change my oil, the oil life monitor still would show around 20 to 30% oil life left. And I drove the car pretty darn hard too (I had a smaller blower pulley on it, so it made pretty good power, it ran 13.7s in the quarter mile)
 
Messages
485
Location
Montgomery, AL
quote:
Originally posted by pgtr: Yes, jjbula, that exception certainly proves the rule that we must all analyze our oils. I'll certainly submit myself to oil analysis reform school [No no] since Camry had a sludging problem.
Hey which finger are waving at me. [Burnout]
 

MolaKule

Staff member
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21,597
Location
Iowegia - USA
And before speedometers and/or oil analysis, many people simply changed oil when the oil became black, which was a good practice in itself, since the older oils did not have the greatest of detergents/dispersants if at all.
 

MolaKule

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Iowegia - USA
from OneQuartLow, "On the other hand, an analysis every change for a recent passenger-car engine has to go in the neurotic/learning/hobbyist category. Pick your poison." I'll pick all three, since I'm really a non-comittal neurotic. [Big Grin]
 

Patman

Staff member
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21,989
Location
Oakville, Ontario
quote:
Originally posted by MolaKule: from OneQuartLow, "On the other hand, an analysis every change for a recent passenger-car engine has to go in the neurotic/learning/hobbyist category. Pick your poison." I'll pick all three, since I'm really a non-comittal neurotic. [Big Grin]
Hehe, I'm guilty of all of the above too! [Happy] Seriously though, some people think I am nuts for spending more on the oil analysis than my actual oil change costs me! But I tell them that it's not so much a money issue as it's a learning thing, it's a hobby, and it really can prevent future problems. If I notice all of a sudden I'm getting antifreeze in the oil, or more dirt, I can take corrective action long before it becomes a serious problem. Plus it allows me to safely do extended intervals. Besides, I figured out the other day that by me doing oil analysis, and if I go with 9k intervals, I'll spend a lot less money per year than if I just went with 3k oil changes and no oil analysis at all.
 

pgtr

Thread starter
Messages
263
Location
tx
"I don't think anyone is saying the statistic-based lights don't tell anything useful" Oh? I'm not sure which bulletin board you're reading but I see plenty of posts that say odometers and lights lack validity all the while barking the tiresome oil analysis mantra. "I don't think we're interested in average lubrication or we wouldn't be here, no?" Since I got over my automotive lubricant retentive stage a couple years ago - sounds like I don't belong here. Thanks. Though I'm an outsider and essentially a heretic that doesn't embrace your oil analysis gospel I'm curious about one thing. What are the specific looming mechanical breakdown(s) you are insuring against by having an analysis done to find the perfect change interval? I figure my silly dependence on private label oils, odos and lights has pretty much doomed me. Just curious what's in store for my cars any minute now...? -T
 
Messages
191
Location
KY
quote:
Originally posted by OneQuartLow: I don't think anyone is saying the statistic-based lights don't tell anything useful, just that they're only part of the picture.
On other boards (particularly those for GM cars), there are plenty of people who don't trust the light, and a somwhat smaller subset of those who cling to the 3 months/3000 miles mantra. My own limited experience (without oil analysis) has shown that their light performs as advertised, illuminating at a reasonable change interval for regular oil (all cars except Corvette). IMO, using any good synthetic in a car whose oil monitor is calibrated for regular oil certainly hedges your bets, and I wouldn't have any reservations about relying completely on the oil monitor interval to replace the mileage interval in that case.
 
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4,805
Location
Lakeville, MN
quote:
Originally posted by pgtr: [QBThough I'm an outsider and essentially a heretic that doesn't embrace your oil analysis gospel I'm curious about one thing. What are the specific looming mechanical breakdown(s) you are insuring against by having an analysis done to find the perfect change interval? I figure my silly dependence on private label oils, odos and lights has pretty much doomed me. Just curious what's in store for my cars any minute now...? -T[/QB]
A couple of things could show up easily - high silicon could show a leak in the air intake system somewhere allowing additional grit into the engine causing excess wear. Or, antifreeze could find its way into the oil, and eventually destroy your engine if not caught soon enough. Personally, I'd rather stomach a head gasket repair than a full rebuild if just a bit of antifreeze was leaking. Lots of other examples. To me, its simply a good way to gain some insight into the condition of the engine other than ot sounds OK, etc...
 

Patman

Staff member
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Location
Oakville, Ontario
Our very own Bror Jace on here found a little bit higher amount of antifreeze in his oil analysis results, so he was able to get the head gasket repaired on his engine before the problem escalated into a much costlier repair. Had he let it go longer, the engine could have hydrolocked and he would've been faced with an entire rebuild instead of just having to do head work. He saved himself a bundle!!
 
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