Oil change algorithm......

[vcode]

So i bought a used 2019 Yukon in February. Oil was changed by the dealer, DIC showed 97% oil life. Fast forward to December and the DIC is down to 18%, even though I have only put 1000 miles on the truck. Most trips have been 15-30 miles and there has been very little idling. My 2010 Tahoe would still have 85% oil life after 1000 miles of similar driving. The old system was not time sensitive though. Does the newer algorithm just deduct 10% or so a month to get to zero after a year of driving? Otherwise I have no idea how I would use 80% of oil life in 1000 miles.

 

[OR VietVet]

IMO, I would change the oil and filter again and reset back to 100% and see what happens. You can also send an oil sample out for inspection and report back.

 

[Jroby42]

So i bought a used 2019 Yukon in February. Oil was changed by the dealer, DIC showed 97% oil life. Fast forward to December and the DIC is down to 18%, even though I have only put 1000 miles on the truck. Most trips have been 15-30 miles and there has been very little idling. My 2010 Tahoe would still have 85% oil life after 1000 miles of similar driving. The old system was not time sensitive though. Does the newer algorithm just deduct 10% or so a month to get to zero after a year of driving? Otherwise I have no idea how I would use 80% of oil life in 1000 miles.

Yes, the system probably has a time component. I have a 2020 XL and only put ~8k miles a year on it. 10% a month sounds about right.

 

[OR VietVet]

Sorry, I missed the 10-11 months in between the oil change and the DIC showing 18%. I gotta look closer. So, in 10-11 months you have averaged approx 8% loss of oil life, each month. That is good, IMO. Also, was it conventional oil or synthetic? Did you keep track of engine hours during that time? What is considered "very little idling".

 

[Marky Dissod]

... bought a used 2019 Yukon in February. Oil was changed by the dealer, DIC showed 97% oil life.
Fast forward to December and the DIC is down to 18%, even though I have only put 1000 miles on the truck.

Your Oil Life Monitor is trying to remind you to change your oil yearly, REGARDLESS of miles accrued.

 

[vcode]

Sorry, I missed the 10-11 months in between the oil change and the DIC showing 18%. I gotta look closer. So, in 10-11 months you have averaged approx 8% loss of oil life, each month. That is good, IMO. Also, was it conventional oil or synthetic? Did you keep track of engine hours during that time? What is considered "very little idling".

The dealer changed the oil so I assume they followed the GM spec. Very little idling means I start it and I go. I don't wait for it to warm up and I have not been caught in any traffic jams. I would estimate 40 engine hours, no more than 50 for sure. I just can't imagine losing 8-10% oil ilfe every 100 miles.

 

[Marky Dissod]

... just can't imagine losing 8-10% oil ilfe every 100 miles.

Unfortunately, changing oil yearly regardless of miles accrued, is a thing according to tribologists.
If you REALLY don't want the Oil Life Monitor to have access to a calendar, consider disabling OnStar.
That way, it will not be able to keep track of how many DAYS you go without changing your oil.

 

[Joseph Garcia]

IMO, you should NEVER change oil based on the dashboard indicator. It is interesting to 'see' it, but that's it. Pick a maximum mileage that you want between oil changes, for many of us here in the Forum 5000 miles is the maximum interval between oil changes for normal driving, and then stick with it, regardless of the time interval between oil changes.

 

[Marky Dissod]

... regardless of the time interval between oil changes.

Tribologists - lubrication engineers - will never - can never - advise oil changes regardless of time elapsed.
For reasons they understand better than us, they strongly advise annual oil changes, even if only to cover their @r$es.

 

[vcode]

IMO, you should NEVER change oil based on the dashboard indicator. It is interesting to 'see' it, but that's it. Pick a maximum mileage that you want between oil changes, for many of us here in the Forum 5000 miles is the maximum interval between oil changes for normal driving, and then stick with it, regardless of the time interval between oil changes.

I changed every 5000 on my 2010 Tahoe. I just don't want to run afoul of my extended warranty.

 

[Marky Dissod]

I changed every 5000 on my 2010 Tahoe. I just don't want to run afoul of my extended warranty.

Back in 2010, OnStar was not adjusting the Oil Life Monitor.
In 2019, I would not be surprised if OnStar was regularly monitoring when your vehicle is used,
adjusting the Oil Life Monitor accordingly.

By the way, I appreciate this thread - it has given me another reason why the last vehicle I'll ever own will be a GMT900.
I don't want my vehicle communicating with anyone else but me.

 

[mjgirard]

I change my oil and filter on my 2001 Tahoe every 3000 miles. Since I only cover about 6000 miles a year that is 2 oil changes a year. To me it is well worth the $50-$60 I spend to keep the oil and filter as clean as possible and I do it myself.

 

[2591tdj]

I just had the exact same issue with my 2019 Tahoe. The DIC said 18% and I received an Email from OnStar telling me it was time for an oil change. It had only 3,000 mostly highway miles on it since the last oil change 10 months ago. I normally have the oil changed with Mobil One every 5k miles but went ahead and had it changed last week.

Apparently, time is factored into the calculation of the remaining oil life.

 

[OR VietVet]

I just had the exact same issue with my 2019 Tahoe. The DIC said 18% and I received an Email from OnStar telling me it was time for an oil change. It had only 3,000 mostly highway miles on it since the last oil change 10 months ago. I normally have the oil changed with Mobil One every 5k miles but went ahead and had it changed last week.

Apparently, time is factored into the calculation of the remaining oil life.

Always has been.

 

[vcode]

I just had the exact same issue with my 2019 Tahoe. The DIC said 18% and I received an Email from OnStar telling me it was time for an oil change. It had only 3,000 mostly highway miles on it since the last oil change 10 months ago. I normally have the oil changed with Mobil One every 5k miles but went ahead and had it changed last week.

Apparently, time is factored into the calculation of the remaining oil life.

Next time just change it at the one year mark. You are getting the notice based on time, not mileage.

 

[PPV_2018]

Back in 2010, OnStar was not adjusting the Oil Life Monitor.
In 2019, I would not be surprised if OnStar was regularly monitoring when your vehicle is used,
adjusting the Oil Life Monitor accordingly.

By the way, I appreciate this thread - it has given me another reason why the last vehicle I'll ever own will be a GMT900.
I don't want my vehicle communicating with anyone else but me.

onStar delete is possible, fyi

But in the context of this thread, the olm is probably not onStar related, it’s probably just set to have a specific time to alert you in addition to mileage.

 

[vcode]

onStar delete is possible, fyi

But in the context of this thread, the olm is probably not onStar related, it’s probably just set to have a specific time to alert you in addition to mileage.

Yep, if you park your truck for a year the OLM will still decrease 8.3% a month.

 

[ReaperHWK]

oil always has a time OR mileage. No oil changes should be longer than 1 year.

Hell, my DODGE needs to have the oil changed every 6 months even if I only drove it 300 miles to keep the warranty. It’s 6k miles OR 6 months with full synthetic.

Oil absorbs moisture and slowly breaks down over time.