GM Oil Life Monitor...How Does it Work?

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AdmiralYoda

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Jan 23, 2013
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Location
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I recently bought a new to me 2021 GMC Canyon with the 3.6L LGZ with 21k miles. Even though the dealer did an oil change before I bought it the first thing I did when I brought it home was to do a fresh oil change since I had no idea what they put in there. I used M1 Extended Performance 5W-30 and a Fram Endurance filter.

I drive 80-90% highway on long trips, 45 miles each way to work. Generally no stop-and-go just continuous highway speeds, usually 65-75mph. I rarely do short trips and hardly ever approach full throttle. No towing and my average fuel economy has been about 24mpg, so I've been driving pretty conservative.

That said, I'm 2,500 miles into the fresh oil change and the OLM is down to about 67%. At this rate I'll hit 0% at 7,500 miles. I'm not complaining because I normally change my oil at 5k intervals, but I am just a bit surprised given how manufacturers like longer and longer OCI's.

So how exactly does the GM OLM work?
 
It's a combination of time and use. I have not idea how it calculates the usage, but my manual says it's based on mileage, operating temperature, RPMs, etc. And the time is a one-year limit. So if you parked it for 6 months, you should expect to see it drop 50%.

I drive my Sierra fairly conservatively with just a little bit of towing, and I'm generally somewhere around 7,000 miles when the monitor tells me to change it (at around 7%).
 
AdmiralYoda said:
but I am just a bit surprised given how manufacturers like longer and longer OCI's.
Click to expand...
Why ? If that's the interval they're calculating, it's fine. Contrary to conspiracy-theory-beliefs, automakers haven't determined how to push oil change intervals so that engines magically explode (3) after warranty expiration because of running oil too long.

Plus, you're using "EP" oil, which promotes longer oil change intervals.
 
Additionally, the Gen 5 V-8 LS Chevy engines will run down to 0 by around 7,500 miles. The Gen 5 engine came out in 2014, and the interval has been similar for the last 9 years. Prior to that they were Gen 4 engines and the OLM would run down to 0 in around 10,000 miles. GM made a conscious decision to move it down from 10,000 miles to 7,500 miles. With that in mind I decided to be more conservative and chose 5,000 mile for my 2008 LY6 engine. YRMV. :cool:
 
The GM OLM calculates an OCI based on idle time, engine revolutions, oil temp, coolant temp, ambient temp, oil pressure, and some other things. If it overheats, the OLM immediately goes to zero, upon reaching 260F.

Since the 2010s, GM also started including hard limits into the OLM: most GM cars from the past 10 years or so will have a max OCI of 7500 miles or one year, except the Volt, which has a max OCI of 2 years and no mileage limit. The hard limits probably started when GM introduced dexos oils, after they had some problems with the HFV6 timing chains from long OCI suggestions.

Older pre-dexos GM cars with the OLM didn't have any hard limits programmed into the computer, but suggested not to exceed a year or 12k.
 
I have a 2017 Canyon with the 3.6. I do some light towing with it (lawn equipment) and I change the oil every 5,000 miles. The OLM usually shows about 20%. I use this schedule because it is a Direct Injected engine. My wife's port injected Acura V6 gets oil changes by the OLM.
 
slacktide_bitog said:
The GM OLM calculates an OCI based on idle time, engine revolutions, oil temp, coolant temp, ambient temp, oil pressure, and some other things. If it overheats, the OLM immediately goes to zero, upon reaching 260F.

Since the 2010s, GM also started including hard limits into the OLM: most GM cars from the past 10 years or so will have a max OCI of 7500 miles or one year, except the Volt, which has a max OCI of 2 years and no mileage limit. The hard limits probably started when GM introduced dexos oils, after they had some problems with the HFV6 timing chains from long OCI suggestions.

Older pre-dexos GM cars with the OLM didn't have any hard limits programmed into the computer, but suggested not to exceed a year or 12k.
Click to expand...
Great explanation.
 
My experience. 2005 Tahoe, OLM usually counts down around 4-5k. I let it idle in summer and winter for heat and A/C, respectively.
 
There are excellent "white papers" online that explain the development of this feature. Google is your friend here.
 
My 2012 Impala was 93 miles per % of the OLM when I had it. I changed every 7500 since it was a company vehicle.

My 2017 Corvette would tick down by time and miles but would always get to zero by 12 months.

My wife’s 2021 Suburban is based on 7,500 miles. Maybe it would go down faster than that in more severe use but that’s how it’s worked out over 44,000 miles.
 
Pretty sure they use a sprinkle of pixie dust combined with two drops urine from a baby unicorn to form an algorithm.

I bought an '05 Canyon new and the OLM first came on at 10,230. However this falls in line with the info in this thread, ie hard limits not implemented until 2010.
 
but if you take your older vehicle in to a dealership and they hook up to your computer, you should get whatever updates GM recommends...one is changing your OLM parameters to that 7500 mile max...or so I've been told

Bill
 
My 2021 Traverse with a similar engine tracks to a 7,000 - 7,500 interval. I have noticed it counts down more quickly with cold weather/short trips. I change at 5,000 for easy math.
 
The engine lab at the Milford MI proving grounds has been used for oil life testing. I was told that they even tested oil filters other than the AC Delco, he intimated that one name brand tested especially poorly but I never could get him to spill on which one. He was a rabid AC Delco filter advocate but never would discuss why.
 
I do know that it keeps track of time passed as well. My 2021 6.6L gas Silverado 3500HD sat through most of last winter and the OLM % dropped pretty quickly after I did the fall oil change. With no miles and only an hour of run time it had dropped about 20% in 3 months.
 
The dealer put in this and it would have been just fine.

s-l1600.jpg


That being said look at this list to make sure you are getting the right oil, odds are you did but it's good to know.


As for the OLM, it very accurate as the data I pulled from Onstar will note. I was only driving 5 miles max in the morning one way in all seasons. Then driving 1 mile to the kids school, then another 4 home. Then I would drive back to work another 5. Then finally home again later. All city, all stop & go. I was lucky to get 4k out of an oil change in this driving style. There was some highway here & there but maybe a 70/30 split favoring city. I would certainly trust the OLM in a GM vehicle now, maybe not so much before but I think they really have it down.

Code: 
Email Date Remaining Oil Life (%) Odometer Reading (Mileage)
03/19/2020 94 58314
04/19/2020 77 59011
05/18/2020 60 59646
06/17/2020 38 61341
07/17/2020 21 62375
08/16/2020 90 63361
09/15/2020 73 64288
10/15/2020 52 65270
11/14/2020 29 66122
12/14/2020 90 66974
01/13/2021 63 67854
02/19/2021 30 68907
03/14/2021 24 69110
04/13/2021 91 70241
05/13/2021 84 71301
06/13/2021 63 72351
07/12/2021 48 73001
08/11/2021 34 73576
09/13/2021 34 73576
10/11/2021 90 74336
11/09/2021 88 74359
12/09/2021 65 75146
01/08/2022 40 75957
02/07/2022 16 76745
03/09/2022 96 77507
04/08/2022 66 78479
05/08/2022 41 79474
06/07/2022 22 80355
07/09/2022 7 81013
08/06/2022 90 81642
09/05/2022 72 82589
10/05/2022 53 83313
11/04/2022 29 84197
12/04/2022 1 85150
 
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