Reported Life of Filters/Oil

[Javelina]

2025 Yukon Denali 3.0l Duramax

Does the reported life remaining for the filters and engine oil actually reflect a measurement, or is it just an hour meter?

 

[2024 White Tahoe]

2025 Yukon Denali 3.0l Duramax

Does the reported life remaining for the filters and engine oil actually reflect a measurement, or is it just an hour meter?

It is an algorithm that uses several factors.

It is also a hour meter, as it will request an oil change after one year, mileage notwithstanding.

 

[Marky Dissod]

It can't analyze oil, but it 'understands' how the engine is being used, and what that does to the oil.

It counts engine revolutions, but it also applies modifiers to those engine revolution counts.
The more time the engine spends at operating temp in overdriven gears with the TCC locked, the LESS revs accumulate.

The more time the engine spends UNDER operating temp, or in lower gears at higher loads, the MORE revs accumulate.
More starts, more cold starts, more short trips, more time idling, more stop'n'go driving, those revs accumulate more quickly.
When enough revs get counted up, the OLM says, 'change oil and filter, already'.

You're supposed to change it @ 15%, by the way, NOT 0%. Can only help to change it sooner, up to you by how much.

Point of the Oil Life Monitor is that, based on how the vehicle is driven / used, 5000 miles may be too late to change oil and filter.

 

[Javelina]

In that case I will be mindful of what is reported. I am pleasantly surprised it is as sophisticated as you describe.

Thanks!

 

[Antonm]

If you want to know more about the GM oil life monitor and how it works, look up the name "Shirley Schwartz" or "Sister Sludge", she's the main person that wrote the algorithm for it. Yeah she had a team so she wasn't the sole person involved in its creation, but it was her idea and her long term project.

Its actually pretty impressive the amount of engineering time and effort that went into it, and an overall interesting story IMHO. Can't imagine the bean counters at GM now would authorize that much R&D money for it today.
...

 

[Marky Dissod]

If you want to know more about the GM oil life monitor and how it works, look up the name "Shirley Schwartz" or "Sister Sludge".
She's the main person that wrote the algorithm for it. Yeah she had a team so she wasn't the sole person involved in its creation, but it was her idea and her long term project.

Its actually pretty impressive the amount of engineering time and effort that went into it, and an overall interesting story IMHO.
Can't imagine the bean counters at GM now would authorize that much R&D money for it today.

Will freely admit that I never read 'Sister Sludge: Behind The Kettering Award'. Will also be the jerk without any engineering degree that asks:
Might it've been simpler to just correlate oil life to MpGs?
The better the fuel economy the longer the oil change interval ... The worse the fuel economy the quicker the interval?
No insult to Dr Shirley Schwartz intended.

 

[Antonm]

Might it've been simpler to just correlate oil life to MpGs?

Simpler , oh hell yeah that would've WAY simpler. But it wouldn't been as accurate or predictive.

The easiest way, which is what the vast majority of auto manufactures do, its just use a milage based approach (the ole "change your oil after X miles" thing that we're all used to). And that milage based approach also cost them $0 in R&D money, hence why most auto makers use it.

GM invested a lot of money into the oil life monitor, and I'm not really sure what their motivation was. Very rarely do big corporations spend money to benefit their customers without a plan to be able to charge something for it or somehow make that money back with extra profit. Seems like the creation of the oil life monitor didn't really make GM any money and might have actually reduced the money coming in their dealerships (which are independently owned, so maybe they don't care about the dealerships).
...

 

[PPK_]

the smaller filter is the 3.0… larger is 5.3/6.2 filter.. the diesel is really not any bigger than a 3 cyl kubota filter.. i can see it is way too small.

 

[Marky Dissod]

Might it've been simpler to just correlate oil life to MpGs?
The better the fuel economy the longer the oil change interval ... The worse the fuel economy the quicker the interval?
No insult to Dr Shirley Schwartz intended.

Simpler, oh hell yeah that would've been WAY simpler. But it wouldn't been as accurate or predictive.

Obviously if two drivers both managed 24MpG with their respective suburbans over 120 days while covering the EXACT same ground miles,
the one that started the engine more times than the other should still change their oil & filter sooner.

I'm agreeing, it wouldn't've been AS accurate or predictive - but I think if Sister Sludge hit the target right between the eyes,
I think my aim would still stay inside the area bordered above the nostrils, under the bottom of the widow's peakpoint, and inside the outer eye sockets.
Determining how much pessimistic bias to apply would likely result in 'me' suggesting an oil & filter change before Sister Sludge would've.

The easiest way ... the ole "change oil after X miles" thing that we're all used to.

Too easy, although it works well enough if used with an intuitive understanding of what Sister Sludge was getting at -
cabdrivers do this better than the general public, the latter choosing very long change intervals despite driving closer to the severe service schedule.

GM invested a lot of money into the oil life monitor, and I'm not really sure what their motivation was.
Very rarely do big corporations spend money to benefit their customers without a plan to be able to charge for it, or somehow make that money back with extra profit.

Y'know how CAFE MpG scoring targets became a thing in the 70s?
My strong suspicion is that Dr Schwartz's algorithm was created to make oil changes longer, so people would feel like they were getting their money's worth.
In the long run this led to superior motor oils, which they charge more for,
leading to more profit for GM & motor oil distributors who cross invest in each other's stocks.

 

[WalleyeMikeIII]

I believe the biggest benefit of the OLM and the research is reduction in the amount of oil used. This research took place during the oil embargo years and led to a reduction in quantity of motor oil used. It also reduced need for maintenance visits, which is a selling point for some consumers…at the time it launched, most manufacturers were recommending 3000 mile oil changes. So being able to stretch this was a huge selling point. Generally I’ve followed the OLM for all the GM vehicles I’ve owned; but now that I own the 6.2 with the 0W-40 scarlet letter, I try to stay around 5000 miles…sigh.

 

[Marky Dissod]

Said this before, it bears repeating.
Spent over 15 years as a NYC livery driver / chauffeur.
In that time, NYC cabdrivers I spoke with noticed that GM's oil life monitor was recommending longer intervals in newer models.
Remember that NYC cabdrivers can drive anywhere between 50 and 200 miles in a day, so they notice how OLMs are behaving across different vehicles.
In the early 2010s the NYC cabdriver consensus was to apply a skew to the Oil Life Monitor's recommendations, as follows:

GM recommends changing oil & filter when the OLM reports 15%, NOT 0%, by the way.
Mostly all highway miles (NOT inside NYC), change oil & filter @ 20%, NEVER over 5000 miles.
More highway than local miles, change oil & filter @ 25%, NEVER over 4000 miles.
More local than highway miles, change oil & filter @ 33%, NEVER over 3500 miles.
Mostly all local miles (NYC, 5 boros, stop'n'go, LOTS of idling, also lots of restarts), change oil & filter @ 40% - NEVER over 3000 miles.

Also, regardless of the above, if/when they detect 0.5Qt - 1.0Qt of oil consumption, they do a full oil change within the next few days, they don't 'add a quart'.
As a result of all of the above, there are plenty of NYC cabdrivers who change their oil monthly, anywhere between 2750-5000 miles, depending.

In other words, it's ok to believe in the Oil Life Monitor, but far better to do so AFTER you apply a dose of Murphy's pessimism to it.

 

[Marky Dissod]

Generally I’ve followed the OLM for all the GM vehicles I’ve owned; but now that I own the 6.2L with the 0W40 scarlet letter, I try to stay around 5000 miles ... sigh.

Just asking:
Ever wonder if you'd save any money by using a 0W30 or 5W30 motor oil, specifically a 0W30 or 5W30 spec'd for GM's 6.6L L8T V8?

 

[Vladimir2306]

Obviously if two drivers both managed 24MpG with their respective suburbans over 120 days while covering the EXACT same ground miles,
the one that started the engine more times than the other should still change their oil & filter sooner.

I'm agreeing, it wouldn't've been AS accurate or predictive - but I think if Sister Sludge hit the target right between the eyes,
I think my aim would still stay inside the area bordered above the nostrils, under the bottom of the widow's peakpoint, and inside the outer eye sockets.
Determining how much pessimistic bias to apply would likely result in 'me' suggesting an oil & filter change before Sister Sludge would've.

Too easy, although it works well enough if used with an intuitive understanding of what Sister Sludge was getting at -
cabdrivers do this better than the general public, the latter choosing very long change intervals despite driving closer to the severe service schedule.

Y'know how CAFE MpG scoring targets became a thing in the 70s?
My strong suspicion is that Dr Schwartz's algorithm was created to make oil changes longer, so people would feel like they were getting their money's worth.
In the long run this led to superior motor oils, which they charge more for,
leading to more profit for GM & motor oil distributors who cross invest in each other's stocks.

Where can I read about GM's official recommendation for a 15% oil life?

 

[WalleyeMikeIII]

Just asking:
Ever wonder if you'd save any money by using a 0W30 or 5W30 motor oil, specifically a 0W30 or 5W30 spec'd for GM's 6.6L L8T V8?

Well. That has crossed my mind. But, the dealer I bought my vehicle from included a “Lifetime Powertrain Warranty” and it is unlimited miles (until the cost of the repair exceeds the book value of the vehicle.). I’ve read the contract, and it specifically says you must follow the manufacturer’s recommended maintenance schedule. Soooo…since this engine debacle happened; I feel blessed to have this “included” (yes, I know it was a lot pack VSC that I paid for in the pricing) coverage. Thus, I’m not going to give them any reason to deny it…

 

[Marky Dissod]

Where can I read about GM's official recommendation for a 15% oil life?

Older owner's manuals for GM vehicles with OLM.
Think the NorthStar & IronBlock LT1 V8s were among the oldest vehicles with OLM, but I'll be pleasantly surprised to learn I'm wrong, as usual.

Sure, motor oil is better today than it was in the 90s, but it's always better to change oil & filter too soon. How much sooner is up to you, I guess.

 

[Vladimir2306]

Older owner's manuals for GM vehicles with OLM.
Think the NorthStar & IronBlock LT1 V8s were among the oldest vehicles with OLM, but I'll be pleasantly surprised to learn I'm wrong, as usual.

Sure, motor oil is better today than it was in the 90s, but it's always better to change oil & filter too soon. How much sooner is up to you, I guess.

There's no point in living by the standards of the 90s. A lot has changed since then. Moreover, the OLM now includes a reserve for excess mileage. I don't remember now, but I think you can drive another 200 or 300 miles after 0%. And nothing bad will happen. I posted an oil analysis at the end of its life; there's still some oil life left.