Strange OLM behavior - 2021 Yukon 5.3

[jfoj]

This graph below should give you an idea of Oil Temps vs Coolant Temp for a 15 minute drive that has few traffic lights and minimal traffic. Pretty ideal conditions overall.

Based on this behavior, you should be able to expect that at 80F ambient this 15 minute drive might only get the oil temp up to 160F!

If I get a chance now that the weather has warmed up, I may try to get another data set for a warmer cold start to see the data tracks.

So this all being said the OLM may actually be pretty good at predicting oil life. Personally I will typically not run the OLM below 50% or maybe around 150 hours. Still trying to figure out the best OCI for my requirements.

At 8274 miles, my engine has 191.45 total run hours. 27.86 "Idle" hours and 48.9 "City" hours per the ECU stored data hours. So this means my engine has 142,55 non "idle" or "City" hours at this point. I have not tried to calculate what percentage "Highway" miles I have on my truck, but I would say around 75%.

As for oil analysis info, I would pay close attention to Aluminum due to the current bearings being bi-metal steel/aluminum. Seems for some reason up to the L84/L87 GM was using coated rod and main bearings, at it appears that GM stopped using the coating on the rod bearings once the L84/L87 were released. Not sure this is 100% the case, but many of the L84/L87 teardowns have coated main bearings still, but uncoated rod bearings.

 

[Z15]

Oil Life Monitor Calculation Pathways:

1. Engine revolutions- Oil life starts with a fixed number of revolutions and will decrease with each revolution. Cold / hot coolant temp readings have multipliers that reduce engine revolutions pathway quicker depending on how far from the normal oil temperature the vehicle is operating.

Note: If engine coolant temp gets above 260F, engine overheat condition, the oil life will go to 0%.

2. Mileage from last reset – Starting with MY 2013, the OLM is capped at 7500 miles for all GM powertrains except the Volt. In perfect conditions a vehicle would reach 7500 miles from the last reset and the oil life left would be 0%.

3. Time- This pathway is a liner function, a fixed decrease in oil life for a given time after the oil life is reset. The oil life will drop to 0% after 1 year regardless of the amount of engine revolutions or how many miles since the reset.



Short trips will make it countdown faster because of the cold to hot cycles being in short duration.

 

[Marky Dissod]

It just freaked me out seeing the OLM go down so fast after such a short period of time.
My plan for this truck was 5,000 mile oil change intervals.

If your OLM says to change your oil before you do, your plans are insufficient.
You should not be 'freaked out', you should be open to learn something.
Whoever you are:
if you change your oil BEFORE the OLM tells you to, that's a good thing.
if you change your oil AFTER the OLM tells you to, that's NOT a good thing.

 

[vcode]

Yea I know another OLM thread. But I couldn’t find one that had similar circumstances. I’ve noticed my OLM going down VERY fast in my 2021 Yukon 5.3.

I changed the oil on 5/10/2025, today is 6/9/2025. So about 1 month ago.

Today after a short drive to and from the grocery store (about 12 minutes each way, 10 miles round trip). The oil life monitor went from 93% to 91% in this trip. Now I reset trip 2 when I changed the oil, and so far on this oil change I’ve only driven 213.7 miles. That equates to roughly 23.7 miles per 1% oil life.

So if I extrapolate out: 23.7 miles x 100% =2,374 miles. That seems way too short for an oil change interval. I know this is lot the exact calculation, just a rough estimate.

In my experience with GM vehicles with OLM systems. It usually is around 65-75 miles per 1% oil life, under normal driving conditions. Extending out to 6500-7500 mile oil change intervals.

Now I know the OLM uses a lot of data to calculate the percentage. Granted our driving so far has been short trips, just to and from the grocery store basically all in town driving. I just feel like something is out of whack.

I changed the oil with Amsoil 0W20 signature and used a Wix filter.

Any thoughts? Am I just overthinking it?

Thanks in advance.

The algorithm also takes time into account as Z15 said. Your OLM will drop roughly 2% a week (or 8% a month), even if you don't drive the vehicle at all, because GM wants you to change your oil after a year. If you are a low mileage driver like I am, it seems strange but that is how it works.

 

[vcode]

If your OLM says to change your oil before you do, your plans are insufficient.
You should not be 'freaked out', you should be open to learn something.
Whoever you are:
if you change your oil BEFORE the OLM tells you to, that's a good thing.
if you change your oil AFTER the OLM tells you to, that's NOT a good thing.

Depends on how many miles you drive. If you only drive 2000 miles a year, the OLM will reach 0% at the end of the year. The oil will be fine in that case.

 

[fondupot]

If your OLM says to change your oil before you do, your plans are insufficient.
You should not be 'freaked out', you should be open to learn something.
Whoever you are:
if you change your oil BEFORE the OLM tells you to, that's a good thing.
if you change your oil AFTER the OLM tells you to, that's NOT a good thing.

Def learning something here. Thanks for all the input.