what does a car computer use to compute oil life remaining?

[BrianApp]

What are all the parameters a car's computer uses to compute oil life remaining, specifically on a 2011 Buck Lacrosse. I thought it would consider, # of starts, time in idle, and in general crank revolutions. I would have thought taking all of this off of the base millage that I can see it would set of the change warning sooner than the recommended 5,000 but it is actually targeting something higher.

Also-

If a car were theoretically started once and run at 60 mph at what millage would the computer show a 0% oil life left?
I am trying to figure out if they are starting with a base millage higher than 5,000 then depreciating that figure with idle time and starts.
I am not sure if the oil life remaining is set too high to make the car seem less maintaince intensive at the expense of engine life but I am starting to think that is what the car maker is doing.

 

[Astro14]

Those would be great parameters, but on a 2011 Buick, it’s probably measuring against a fixed number of hours and/or miles to get to % life remaining.

E.G. it’s tracking miles vs. 10,000 (as nominal oil change interval) and it’s tracking hours vs. 400 (as nominal oil change interval) and displaying the lowest percentage based on those two parameters.

 

[BrianApp]

So the target on this car is the lowest of10,000 miles or 400 run hours? If that is all this feature is quite a waste. Counting actual crank revolutions and # of starts shouldn't be too hard.

 

[demarpaint]

A short answer to your question. An algorithm, that may or may not be accurate.

Common sense and decades of car ownership led me to back check mine with a UOA or two to confirm its accuracy before I'd trust it on blind faith. As it turned out for me ignoring it from day one was a smart move.

 

[Astro14]

So the target on this car is the lowest of10,000 miles or 400 run hours? If that is all this feature is quite a waste. Counting actual crank revolutions and # of starts shouldn't be too hard.

It's a guess on my part, but I doubt those other things are counted.

The OLM in a 10 year old Buick is a rudimentary device at best.

 

[BrianApp]

I am also going to use standard OCI as it seems to be targeting something much higher.

I would like to see the long answer though with the parameters and formulas it uses if anyone knows how this computer was programmed.

 

[Astro14]

I am also going to use standard OCI as it seems to be targeting something much higher.

I would like to see the long answer though with the parameters and formulas it uses if anyone knows how this computer was programmed.

Again, I think you're wishing for something (algorithm, multiple parameters) that simply isn't there.

I think all this car has is a rudimentary counter. Miles. Hours. Hours if you're lucky. Might just be miles and days.

No better than the counter on my Volvo, which adds up miles and days. When it hits 7,500 miles, or 365 days, it says, "Service Due". That's the sum total of sophisticated algorithmic parameter evaluation. Doubt GM put more thought into it than that when the car was designed over a decade ago.

 

[slacktide_bitog]

Different systems use different parameters.

For example, GM takes into account oil pressure, oil temperature, coolant temp, ambient temp, idle time, engine revolutions, etc. Later GM OLM's have a base of 7500 miles and a 1 year limit. The percentage goes to zero as soon as either of those milestones are reached. The exception is the Volt, where the max is 2 years and no mileage limit. It also drops to zero immediately if the engine overheats and reaches 260F.

These limits started around 2011, when they started using dexos oil and more heavily using DI across the board. Prior to that, the OLM didn't have any hard limits programmed into the computer. The 3.6 V6 with DI had problems with long OCI's suggested by the computer, which is why they implemented the limits and switched to dexos.

Mercedes mainly goes by how much fuel is consumed.

 

[jrvn]

mileage

 

[JohnnyG]

Mercedes mainly goes by how much fuel is consumed.

Or one year, whichever comes first.
As to the GM OLM, it was never a "rudimentary" device. Even back in 1999, the one on my STS was a very useful tool and would follow all of the parameters as described by slacktide, and possibly a few more. Yes, there had to be adjustments made to the algorithm over the years due to different engine designs and parts suppliers.
This subject has been written about on this site so many times, I'm really not going to go over it all again. I will say the my first reply on this subject was around 2005 when I let my Oil Life Monitor on my 2004 Chevy truck go to 12,000 miles and sent a sample to Blackstone. The report said that it had several miles of life left.
Just Google GM OLM and try to get the full story from GM. The woman engineer that devised the thing did a fantastic job. There is a patent on it of course, and none of the other car makers have been able to come up with a similar or better system of predicting YOUR oil change interval.

 

[Cujet]

My 2009 F150 uses 6 months or 7500 miles, which ever comes first.
My 2011 F150 seems to simply use 7500 miles.
My 2018 F150 seems to simply use 10,000 miles.

On the two newer ones, (which do sit for periods of time) we reset the trip meter when doing oil changes. The trip meter matches the percentage perfectly. 5000 miles on the 2018 equals 50% oil life remaining. At which point, I change it.

 

[nomas]

My Titan uses a 5k mileage counter . Works just fine for me .

 

[BrianApp]

I get lots of generalizations but not the specific formula and code. I was wanting to see a list of parameters and the actual formula used in the code. All of the ariticles I find by searching GM OLM dumb it down and just give a list of things it probably tracks and that's it. Usually when I ask a question like this there is always someone in the world who knows the exact answer and has experience with it. Somewhere out there there is a person who designed the program and would be proud to see the interest and explain his or her design process and formula. I know if I was on the design team I would enjoy seeing the interest in my work and love to expand on all the details. The article with the designer has probably already been written I just haven't found it yet.

 

[Astro14]

I remember seeing a discussion on GM OLM in about 2015. And it was a sophisticated algorithm. Coolant temp, miles, fuel, all of that. But that’s four years after the OP’s car was built.
OP - if you want the exact algorithm, I expect its proprietary.

Several threads here on the GM OLM with UOAs when it hit 0% showed that it works well.

 

[Just a civilian pilot]

My 10 year old Honda ( 2012 but door sticker says made in spring 2011 ) MM OLM seems pretty smart and varies widely depending on type of driving. The Longest it will let me go with my type of driving is 12000 miles and around 7500 when mainly city and idling a lot.

It penalizes me when I drive faster. They raised the speed limit on the highway I use to go to work and I notice it’s less generous and says to change the oil more often. I trust it totally.

The OLM in mine certainly isn’t sacrificing engine life to lower the scheduled maintence to make Honda look like a cheaper car to own and operate.

Some people just don’t trust extended drains even when the manufacturer says they are safe when following the OLM. Not saying every one is accurate ( how would I know ) but an UOA would help them find that out.

 

[BrianApp]

Yeah, I guess it would be like a PID loop control. All the research and quality of the controller come down to software and not the sensors. I was just looking to get a sense of the thought that went into it. With access to all of the sensors that a modern car has it could be very useful and accurate in determining oil wear or it could just be an idiot light that looks cool in a dealer showroom demo.

 

[skrypj]

My 2011 Lexus GX just triggered its light at a little over 5000 miles even though the manual says 10k. Other than towing a trailer about 350 miles, it lives a pretty easy life.

 

[samven]

The problem with all of them is they dont know what oil you started with. If they assume you have the absolute cheapest, lowest quality oil that will meet their spec you get one answer, if its the oil that the manufacturer used you would get a different answer and if its a top shelf high quality oil that exceeds all their specs yet another. And they have no way to compensate for the changes in API specs so good or bad going from SM to SN to + to SP might affect the outcome because additives change.

 

[4WD]

OLM was invented by Al Gore … he then hired a rhythm consultant

 

[JohnnyG]

BrianApp, I don't think GM, or any company for that matter, is going to publish a detailed description of how their proprietary system designs work. I'm sure they spent plenty of money and time developing the algorithm and how each of the sensors contributes to achieving that result.

samven, I also think I see what you are trying to say here, but I think the only assumption that GM is going to make as far as oil choice goes, is that it meets the specifications called for in the owners manual. Cheap or expensive is up to the individual. And the good thing about API specs is that they are mostly backward compatible, so if your engine calls for SN+, that's what should be in it.
But you are right, the OLM does not analyze oil or know its quality, or how old it is, or even if the OLM is reset properly. It also does not check the oil level, that's a different sensor altogether. It just does it's thing just as if the owner knows how to follow the owners manual.