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Discussion Starter #1
I have no idea how the oil life monitor decides when the oil needs changed, GM says it monitors a lot of parameters but is vague on details... Oil changed last October, (first oil change, 19' Denali) Dealer did the change and I verified the OLM was reset. We didn't use the car much over the winter and when we did it was for relatively short trips so I'm guessing this was a big factor but I still didn't expect 74% of the oil life would be used up in just 2,200mi. I plan to change the oil myself this time so I can be sure it gets full synthetic dexos as I think the dealer uses a bulk blend. Anyone else see shorter than expected intervals for oil changes?... I'm not complaining as I know good quality oil changed frequently will help extend the life of the little turbo DI engine. Oh, 1st oil change was done just shy of 3,000mi.
 

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I have no idea how the oil life monitor decides when the oil needs changed, GM says it monitors a lot of parameters but is vague on details... Oil changed last October, (first oil change, 19' Denali) Dealer did the change and I verified the OLM was reset. We didn't use the car much over the winter and when we did it was for relatively short trips so I'm guessing this was a big factor but I still didn't expect 74% of the oil life would be used up in just 2,200mi. I plan to change the oil myself this time so I can be sure it gets full synthetic dexos as I think the dealer uses a bulk blend. Anyone else see shorter than expected intervals for oil changes?... I'm not complaining as I know good quality oil changed frequently will help extend the life of the little turbo DI engine. Oh, 1st oil change was done just shy of 3,000mi.
I believe one of the parameters that GM uses is time. If one would plot it out it, I think you would see an exponentially DECREASING curve on time vs. mileage. I've read that no matter how few miles you've put on, after one year since the last oil change the OLM will read 0%. So after close to 8 months after your last oil change, it's really no surprise you're down to 74%.
 

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I believe one of the parameters that GM uses is time. If one would plot it out it, I think you would see an exponentially DECREASING curve on time vs. mileage. I've read that no matter how few miles you've put on, after one year since the last oil change the OLM will read 0%. So after close to 8 months after your last oil change, it's really no surprise you're down to 74%.
Don't know how to edit on this new format, meant to say that your OLM must indicate 26% oil life left with 74% used up.
 

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I believe one of the parameters that GM uses is time. If one would plot it out it, I think you would see an exponentially DECREASING curve on time vs. mileage. I've read that no matter how few miles you've put on, after one year since the last oil change the OLM will read 0%. So after close to 8 months after your last oil change, it's really no surprise you're down to 74%.
Right you are, I had the same problem when I took my Encore in last year for it's first free oil change.
I have known my Service Advisor since 1999 when he was in the GM Apprentice Program, he gave me the straight scoop.
You can edit by clicking on the three small dots on the top right of your post.
 

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Discussion Starter #5
If time is part of the logic then indeed it would make sense that I'm down to 26% remaining. I've had OLM's on two other GM vehicles however that did not use time as part of the logic, most recently an 08' Silverado. I put very few miles on that truck and the OLM wouldn't go to 0% remaining after one year with just a few thousand miles driven over that time period
 

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If time is part of the logic then indeed it would make sense that I'm down to 26% remaining. I've had OLM's on two other GM vehicles however that did not use time as part of the logic, most recently an 08' Silverado. I put very few miles on that truck and the OLM wouldn't go to 0% remaining after one year with just a few thousand miles driven over that time period
The idea behind it is in the Owners/Warranty Manual.
Regardless of mileage, you have to do an oil change once a year as a condition to keep the factory warranty in force
 

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Discussion Starter #7
The owners manual does not specifically say the OLM will count down to zero based on a one year time frame whether or not the vehicle is driven. In fact I don't believe it mentions "time" at all.. It does mention driving conditions, load on the engine "towing, hills" temperature, short trips, idle time etc. So based on the OLM, if I leave my terrain in a temperature and humidity controlled garage for one year w/o driving it, it will tell me I need an oil change.
 

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Discussion Starter #9 (Edited)
Great article, thanks for posting... The article was published in 09' and makes no mention of calendar time being part of the calculations... Still a great article
 

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The "Thesis" is nearly 11 years old and am pretty sure Oil Life Monitoring has progressed since then in scope and algorithm. It was a graduate work based on then current data.
I do know that GM, since then, has several times reevaluated how OLM is accomplished.
For one, even with the use of synthetic engine oil, I notice our 2019 vehicle drops in percentage much more quickly than in our both our other GM 2017 vehicles. Even in warmer weather like now after resetting the OLM on our 2019 Acadia the percentage will drop 15% or more in just a few weeks or even 200 to 300 miles or so.
And, the oil still is new and no where near the visible condition of "dirty oil".
It's also notable and interesting that OP noticed his 2019 Terrain
Oil Life also dropped fairly quickly.

So I suspect, with the use of gasoline direct injection and fuel dilution of the engine oil plus other factors, that the newer vehicle OLM is less generous with how long the oil life should be.

It's also notable that our 2017 Colorado truck and 2019 Acadia both have the same 3.6L LGX V6 engine in them yet the Acadia "ages" the oil at a much faster rate. Granted, who knows what other factors might be included in the OLM formula, but it is interesting.
 
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Due to the pandemic, I have only driven about 200 miles in the past 3 months. I changed my oil a couple of weeks in to the pandemic (full synthetic and a new ACDelco filter) and reset the OLM. OLM doesn't consider oil type and filter. I noticed it is already down to 94% remaining...so 6% "used up" in only 200 miles. There must be some sort of time consideration in the algorithm, because at this rate it will be down to 0% around 3,500 miles. I usually see up to 7,000 miles before getting to single digits on the OLM during my normal driving habits. Now, we are expected to return to the office full time over the next couple of weeks, so I will have to see if the OLM slows down as I return to my normal commute.
 

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Discussion Starter #12
I would think if you changed your oil and left the car in a garage, even for a year.... it would NOT need an oil change. If you did a lot of short trips in a cold climate and THEN put it in a garage for a year then yes, it would need changed.. JMO... I realize no OLM can be perfect and they do not monitor oil quality or degradation of the oil. It's a "best guess" system but it's still very good and I'm sure it's more advanced than when the above article was published. I keep track of miles driven as well as checking the OLM all the time so it will be interesting to see what the mileage will be when the OLM reaches 20 or 25%.. Because I have the 2.0 DI engine, I plan on always changing the oil long before the OLM tells me to. On our 02' Buick regal I can go 5,000mi. before the OLM gets down to 20% remaining. The buick has a V6. It's probably a good thing for these little four cylinder DI engines to have the oil changed more frequently, I assume most owners wait for the OLM to tell them it's time to change the oil unlike most here who seem to maintain their cars a little better. The oil on my dipstick still looks very translucent and does not smell of gasoline however it is a little darker than when it was fresh. I hope other forum members will post how many miles (or months, or both) they go before changing the oil. One thing I do notice is that on relatively long trips (over 100mi.) the OLM will not decrease while driving but the next time I get in the car, it has dropped one or two percent. This could be because of the miles driven or the fact that I hadn't driven the car for a few weeks after the trip. I still can't find any published information that says the OLM also considers time as part of it's calculations. I plan on keeping the car for a long time so I'll find out sooner or later. I also find it important to charge the battery if the car isn't driven for a few weeks. A new AGM battery in good health should only self discharge at a rate of 1-2% a month and ours will be down 10% in a month, most likely due to the anti theft system and other systems that occasionally "wake up" when the car isn't being driven. No lead battery likes to be left in a partially discharged state for long periods of time
 

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My oil was changed 12-12-19, has 2,010 miles on it and OLM shows 51%
The car has not been out of town since the last week of Feb and only driven a couple miles at a time since then.
I had a new battery installed March 13th and have driven 390 miles since then.
Short trips will count down the OLM faster.

My wife's 2008 Malibu had it's oil changed 2-5-20 and had 61,300 miles on it.
Her car has not been out of town since then and she drives 2 miles to work.
The other day she mentioned the Malibu had 62,000 miles on it.
I'll try to remember and check her OLM after she gets off work.
 

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On page 49/50 there is a correction factor for time, 24 months. Maybe its been improved upon, but interestingly in the owner's manual for my '11 states " the engine oil life system might not indicate the need for vehicle service for more than a year."
 

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On page 49/50 there is a correction factor for time, 24 months. Maybe its been improved upon, but interestingly in the owner's manual for my '11 states " the engine oil life system might not indicate the need for vehicle service for more than a year."
On our other two 2017 GM vehicles which did not get driven much last year, the Onstar monthly vehicle status indicated they were due after the oil was in 12 months . . . no matter the mileage.
One only had about 2,600 miles and the other 3,880 miles.
 
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On our other two 2017 GM vehicles which did not get driven much last year, the Onstar monthly vehicle status indicated they were due after the oil was in 12 months . . . no matter the mileage.
One only had about 2,600 miles and the other 3,880 miles.
Interesting that GM has made changes in the oil change policy through the years.
This is a direct quote from page 11-3 of the 2014 Equinox Owners Manual.

"The engine oil and filter must be changed at least once a year and the oil life system must be reset."
 
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My wife's 2008 Malibu had it's oil changed 2-5-20 and had 61,300 miles on it.
Her car has not been out of town since then and she drives 2 miles to work.
The other day she mentioned the Malibu had 62,000 miles on it.
I'll try to remember and check her OLM after she gets off work.
After four months, 740 miles her OLM shows 78%
 

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"The engine oil and filter must be changed at least once a year and the oil life system must be reset."
The Owner's Manual for my '18 Terrain says the same thing, with a preceding sentence that reads "It is possible that, if driving under the best conditions, the oil life system may indicate that an oil change is not necessary for up to a year." The Owner's Manual for the wife's '13 Caddy ATS has the same two sentences.
 

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Discussion Starter #19
What I would like to see if anyone can verify is if the vehicle isn't driven for say 36 days, does the OLM correspondingly show 10% less oil life remaining
 
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