When it gets to 1% I call for an appointment. I drive a lot so my mileage prioritizes over the one year time. It is at about 7,500 give or take a few miles.

Thanks, as a "gearhead" since I started reading Hot Rod etc etc when I was ~12 years old cars have always been my hobby! A technical relief from the day-to-day technical work issue in my area of expertise, the welding business!

The was a fellow who worked with the PhD at GM who developed the system. His forum name was BobIsTheOilGuy. Might want to search his posts from several years ago. He stopped posting because too many folks told him their "changing at xxxx miles or whatever was better! His posts went for pages and he talked about measuring for zinc dialkyldithiophosphate, is an anti-wear compound comprised of zinc and phosphorus. Then how they modified for sever service factors etc.

Frankly not sure that old material is still accurate as GM no doubt has improved it since then but he convinced me of his bottom line - the system is based on science and is conservative.

I have a 2014 z51. I Blackstone my oil regularly, especially as the vehicle gets older.

Once I left home in the z51 expecting to drive 6000 miles before I got back so I installed brand new 5-30 Mobil One the day before I left. I had to stay unexpectedly at my destination for an extra 2 weeks, and that increased my expected mileage to ~7100 miles before I got back home. The DIC gave me an "Oil 0%" about 180 miles from home, so by the GM algorithm, my oil was supposedly done at ~6920 miles of use. Once I got home, I dropped the oil immediately and sent a sample to Blackstone. The odometer read just over 21,000 miles. Blackstone said the TBN value was 5.4 and they recommended that I could have waited for another 1900 miles and changed it out at 9,000 miles and still be well above safe TBN levels.

Now I run oil changes according to whatever Blackstone recommendations. None of my three vehicles' oil lasts less than 6500 miles; that hasn't taken more than a year in any vehicle.

Yes, it's an algorithm that uses both time milage, and how hard the engine has been driven. I usually change around 10% myself

I would also hazard a guess that the OLM is very conservative just for warranty purposes. No way GM is going to take ANY risk.

My Mercedes SLK 55 AMG used European spec Mobil 1 and their mileage counter was about 15,000 miles.

And besides the additional out of pocket cost, there's the time you have to spend sitting around a dealership waiting for your car.

Mine sat over the winter and my first drive, 4 weeks ago indicated 50% expiration even though it was never driven. Should I push it to the full 5000 km's?

I agree. No reason to get into a debate with GM regarding oil changes. The LAST thing they want is to have their engines grenading under warranty. A smart owner doesn't risk jeopardizing engine warranties. Just change the shit when the car says to.

I absolutely agree the system is conservative. It makes perfect sense from a customer satisfaction and warranty cost point of view for GM to have a generous safety factor in the algorithm. To me, it makes sense to run the oil until the OLM nears 0%. Changing it with 20%, 30% or whatever left is adding a safety factor on top of a safety factor. It is unnecessary and a waste of time and money.

exactly!!

At my convenience. I'm not going to try to get to 0%. When it gets within 10% I'll have it done. I'm going on a trip that will probably exceed 3,000 miles next month. If I don't get it changed before I leave it will get to zero in the middle of the trip. It makes sense to do it before I leave. No need to be OCD about this. Just get close.

I do not pay any attention to the OLM what so ever. My car is a daily driver 12 months of the year and I put about 13,000 miles on annually . I check the oil level about every third fill up and change it when it looks dirty. I'm guessing that might be at about the 5,000 mile mark ,maybe about 30 -40 % left on the OLM

Kerbeck told me 20-25% and never to get it get below 15%

Would those be the same folks who gave us the oil-gulping 2001 engines, the disintegrating harmonic balancers, the problematic A8 transmission, etc? They are good engineers, but not perfect.

With the 5W-30 Mobil 1 most of us have been using, there is enough experience that I'm ok with running down to 0% but usually change somewhat sooner just for scheduling convenience.

When I switch to the 0W-40, I'll be pulling a sample for analysis at 50% and changing at 30%, until we get more real world experience with that oil in these engines.

This really bothers me. The oil life monitor pushes to have an oil change within a time period as well as mileage.

It seems a waste to change the oil with less than 6000-8000 miles on Mobil 1, just because a year expires.

I still change annually, but to see it go to 0% with only 3000 miles is ridiculous.

^^

Hmm, have provided this info in a number of posts in a number or Threads on the subject - but to repeat!

All 5 of my Vettes have said change at a minimum of once per year in the Owner's Manual! The C7 just keeps track of time for those who never read it or didn't want to believe it!

This is what it said in my '93 Vette Owner's Manual.
1) Change at 7500 miles OR one year which ever comes first.
2) If most Trips are under 4 miles change at 3000 miles or 3 months whichever comes first!

In '93 the only thing measured was miles and they had to guess what to do IF you mostly made short trips.

The worse thing for oil is starting, not letting the oil get to temp (175 to 190 F) for long enough to evaporate some of the excess products of combustion that pass cold pistons. One main product is water that will form acids etc. To keep a cold engine running they also use a richer fuel/air mixture so that also passes the cold pistons that have more clearance to the cylinder walls until the pistons get hot. In fact the worse thing is pulling a car out of the garage to get something it is blocking and putting it right back!

Because it seams a waste to you is as bad as changing when it "looks dirty!" :crazy:

Your car do as you wish but don't expect GM to honor the warranty IF you have problems.

If you're changing your Mobil 1 full synthetic engine oil at less than 10K miles, you're changing it before it needs to be changed. Oil filter changes notwithstanding. 15K miles is probably closer to the miles it would need to changed.

My C7 OLM must be broken.:yesnod: My C7's crankcase oil was installed in 2016, is still @ 67% last I checked. With 1,300 miles on the car, approaching 2-years of age, by GM Standards it should have blown up by now. :lol:

Brilliant Joe, what do those GM engineers know! :crazy2:

No it won't blowup but the acid etc formed in the oil is corroding the metal parts. Your car do as you wish!

If the OLM actually isn't saying change there is something wrong but expect from the way you are saying it and the illogic in many of your posts you're zeroing it out! :crazy2:

Amazes me that folks will spend ~$60,000 for a car and not want to change oil once a year!

Above another example of the below: