Oil Life Calculations

ctuinstra

Goblin Guru
I found this interesting on how the end of oil life is calculated on models 2010 and newer.

Engine Oil Life Monitor Operation Calculation 2010 - 2017 All Passenger Cars And Light Duty Trucks with Oil Life Monitor System This PI was superseded to update Model Years. Please discard PIP5282. The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI. Condition/Concern Since 2010 all GM vehicles have been equipped with the oil life monitor (OLM) system. The monitor calculates the percent of oil life remaining, based on 3 pathways.

The OLM starts its calculation for all pathways after the first 50 miles to account for marshalling and time before sale. Subsequently, calculations begin immediately after each reset. Recommendation/Instructions 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. The oil life will drop to 0% after 1 year regardless of the amount of engine revolutions or how many miles since the reset.
 

Brian74

Goblin Guru
Familiar read. My dd is a 2001 Saturn SL with 217k miles on it. I bought it at 157k and rebuilt the entire car minus engine/trans. The GM oil life monitor system was in its primacy around then. I change my oil every 3k. OLM light usually hasnt come on yet and I have to reset it later. Consensus says ignore it and go by mileage. I think GM incorporated it as a way of reminding the mechanically ignorant in common English language on dashboard to change their oil. Its obviously lame technology that prevents GM from having to address early warranty claims due to pure maintenance ignorance.

If I can find the 2001 link regarding the GM OLM I’ll post it. It reads similar.
 
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