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Discussion Starter · #1 ·
Neighbor has a 17 bought it new has 7k miles roughly & has had the oil changed 3 times because the oil life had dropped to 5%. Is it possible that the oil life drops with the truck just sitting?
He only uses the truck to haul his horses it's usually longer trips.
 

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Neighbor has a 17 bought it new has 7k miles roughly & has had the oil changed 3 times because the oil life had dropped to 5%. Is it possible that the oil life drops with the truck just sitting?
He only uses the truck to haul his horses it's usually longer trips.
He's had it for 3 years and it wants to be changed once a year?
 

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2018 Chevrolet Silverado 2500HD WT, 6.6 Duramax (L5P) Crew Cab 4x4
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This is one of the calculating factors.
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.
 

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He gonna be bummed about that, he's tighter than a charlie horse.

Tell him if he doesn't want to change it he can just reset the OLM.

It's based on engine hours, heat/cool cycles, power levels, engine temperatures, time, and maybe a few others.


It does NOT sample the oil.
It also doesn't know what type of oil is used.

Leave the dirty oil in or use the best available, and it still calculates assuming the oil used is what the manual recommends.
 

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Discussion Starter · #6 ·
What year did the monitor start working like that? Are they like that on gassers too?
 

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Not sure when but my 2016 Corvette Z06 uses calendar time as part of the equation. I change the oil in late October right before it goes into winter hibernation and when it wakes up in March the OLM will be in the 70% range with no engine operation. Not sure about my 2014 Cadillac ATS because I drive it frequently enough.

This calendar type algorithm is used on all newer GM vehicles. I much preferred the old system where it only tracked oil degradation due to operation and depended upon the owner to track yearly changes for infrequently used vehicles. As an alternative I would prefer it just do its major drop as the final month of the 12 month period goes by but I guess GM didn't want customers freaking out over a rapidly declining OLM index.

It is a good but not perfect system; my 2008 Cadillac CTS was recalled and reprogrammed early in its life by GM because the original OLM system called for excessively long change intervals and the engines started eating timing chain components. I always do a 1,000 mile change for both the oil and axles and for that Cadillac thereafter I changed the oil and filter at 50% and again when it got near 0% at which time I would reset the OLM. After GM recalibrated the OLM, the new change interval was about the same as what I had been doing previously.

Given "new GM's" inability to properly solve shudder with the 8Lxx series transmissions, failing wheels on the C7 Z06 and GS, or the flawed CUE system and leaking axle seals with Cadillac my faith in their engineering prowess isn't what it once was.

Rodger
 

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As long as they've had the OLM, but I think they have ramped up the weighting of the 'time' thing. (Perhaps so it matches the OM recommendation on low usage vehicles)


They have been known to 'tweak' the calcs it uses on different engines.

Yes, gassers are the same.

When they introduced it they got awards/praise in the engineering community for it.


I had read SAE papers about it, but was still a sceptic til I found one one of my vehicles that the 'mileage to recommended change' did change on MY vehicle when my usage of the vehicle changed.


Since each engine model has characteristics that are different, each one will have different weighting on the factors used in the monitor.



FWIW, fuel filter measures the restriction of the filter -- so resetting it does work like the oil life monitor. (at least the LML did)

OM also says fuel filter change should be OLM, but not to exceed 22,500 miles, and not to exceed 2 years.
L5P fuel filters don't seem to last that long, but on LML it was/is common to hit the 2year and/or 22,500 miles on one filter.
 
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