JerryU

Hmm, obviously not reading any of the posts with info that shows it IS NOT A TIMER!"
I'll try to explain, perhaps not for yourself but the other ~700 "silent majority" who have visited this Thread but did not wish to post!

GM used a timer in the C7 since it is obvious from reading some of these posts a number of Vette owners never read or understood the prior info in Owner's Manuals as I published for my 2008 C6 (and other Vettes) in post #31 ! You always had to change oil based on OLM, mileage OR ONE YEAR WHICHEVER OCCURRED FIRST!

Those who are all concerned because GM doesn't have the time somehow related to miles driven when in fact that makes no difference as at the end of a 12 months from the prior change it would say a change is needed. Unless you changed the oil just before the Vette was put away and did not start the engine, the oil is already contaminated! Start the car even once and with cold pistons, combustion products get past the rings. In fact starting mixtures and cold operation are also rich, i.e. have excess fuel. That means raw gasoline, CO, CO2, water and nitrogen oxides are mixed with the oil. These form acids (and other things mentioned in my prior post #37, quoting BobIsTheOilGuy.) That "crap" is in the oil and eating away at whatever it is touching in the engine even when it it is not running! The oil in your crackcase is NOT like the uncontaminated oil in a container on the shelf!

Therefore there is even logic in using time when the engine is just sitting! In fact, a start is MUCH worse for the oil than highway mileage put on when the engine is hot!

As many have said, your car do what you wish! Hopefully the "silent majority" who don't post and are reading the last post on this Thread are not left with "It's just a TIMER!"

Boiler_81

It’s pretty simple. If you are not degrading the oil as measured by the algorithm at a rate which will take it to 0% in less than a year, then time is the governing factor. In this case, the monitor will drop the percentage of life left at a rate which will bring the monitor to 0% from the date it was last reset. If this is your use case, the OLM is acting as a timer. It is however not a “simple timer”.

If the monitor sees conditions which degrade the oil at a rate which would bring it to 0% in less than a year, the monitor will reflect a rate which is less than a year. In this case the algorithm is calculating oil life based on the run factors previously mentioned.

Over the years there have been many debates on this forum on the validity of the OLM. My feeling is an algorithm based on engineering study is superior to old rules of thumb. Therefore, I follow the OLM.

If people want to change oil based on whatever belief they have, that’s their prerogative. As long as it is before the OLM indicates the need for the change, no issue. It’s their time and money. However, if you are stretching beyond the OLM change indication, GM has the right to deny warranty coverage. Personally, I think it’s a small price to pay to know my powertrain warranty is in place.

dbaker

Not going to debate the usefulness of the OLM.Just sayin'....

Tues I had the oil changed at the dealer in my '17 Z51.Drove it 1.8 miles and parked it in the garage.
Snow here in SC,so it's been parked since Tues.

OLM is at 98% today(Sat).

That was a quick 2% loss.

\db2

Patman

I have a suggestion for those of you that drive low mileage per year (under 2k for instance) When you drain that Mobil 1, catch it in a clean container and re use it in another vehicle (if you've got an older car out of warranty that takes 5w30 that is) That way you're treating both of your cars to a good thing, your older car can run that M1 for an extra year no problem.

NSC5

With no car operation the OLM should decrement around 8% per month if GM's goal is a smooth decrease based upon time and that seems to be the case given what people report with the OLM decrease after the car has been stored for a few months. So a car stored for 6 months would have close to a 50% hit against the life according to the OLM.

Next the owner takes it out of storage and puts significant miles/hours/operational load on the car and in the next two months sufficient to cause the OLM algorithm to issue an additional 50% reduction in oil life resulting in the indicated need to change oil.

Under the prior system that registered only operation and required the owner to use a calendar to ensure at least a once per year change he would still have 50% oil life remaining according to the OLM. With the new system only half of the previous change interval operational hours resulted in dropping the OLM remaining percentage to 0 even though it is still well under the one year period.

For most of us the OLM system works very well and just like every other feature of the car it is designed for how the majority of the market uses it, i.e. this explains the less than robust cooling system of the Z06. GM also understands that many people ignore maintenance so putting the calendar reminder function into the OLM algorithm makes sense although I suspect the "normal" Corvette owner is much more attuned to preventive maintenance compared to the average car owner. I use the OLM and given the price of oil I don't mind being penalized by an additional change if my storage (midwestern winter with Z06) plus driving habits don't perfectly fit the standard owner profile used to develop the OLM.

In general the OLM is a great system when the General gets it right. I am glad I didn't listen to it with my 2008 CTS or I probably would have had the same timing parts issues that many had with the first gen 3.6L DI engine and its ridiculously long oil change interval. I would rather change too often rather than too infrequently. But in terms of accuracy I suspect the older OLM algorithm was more accurate than the current one for owners who observed proper procedure but dumbing the system down for dumb owners makes sense for GM in order to avoid the idiot who puts low miles on a vehicle and ends up with 4 year old oil in the system.

JerryU

Doing the math, 5 days/365 = 1.4%. But traveling 1.8 miles you did not come close to getting the oil hot enough to evaporate the extra blowby from the engine start! So the algorithm could have taken that into consideration. If it went to 1.5% that rounds up to 2%!

A start without getting the oil hot to evaporate the unburned fuel from the rich cold engine mixture, excess combustion products, i.e. CO, CO2 and water that passed the rings because the pistons are cold is probably more a degrading factor than 1.8 miles! Just Sayn'

PS: Could never convince the wife that those 2 mile trips to visit girlfriends was not great for her Porsche Cayenne! Doubt I'll convince many on the forum but dry sumps take loner to get the oil up to operating temp! It also needs to be there long enough to evaporate the water, the major product of combustion. The water forms with CO, CO2 and other combustion products to form an acid. Not good!

NSC5

Once I start a vehicle it is going to be driven long enough to get the fluids up to temperature and the OLM algorithm rightly places a heavy penalty on short trip operation especially in cold weather.

And Jerry I agree with you about the dry sump oil temp being important and I am surprised that GM used coolant instead of oil temperature to drive the shifting yellow/red zones on the tach during warmup.

I always try to get vehicles reasonably warm before putting them under load and several times while traveling in my diesel pickup I would put a few miles on it driving around after an overnight stop before getting on the interstate merge ramp. It wasn't absolutely necessary but I don't like beating on a cold powertrain.

vettetwo

I agree 100% with your comments about dry sump. When I ordered my 2014 it was supposed to be a Z51. The dealer was unable to get a Z51 and I changed my order to a regular Stingray. One of the reasons I am happy it came out that way is that the oil in my wet sump heats up much faster. I always drive at least 10 miles to completely warm the engine, and it is fun to do so. When I order the next one, I may very well get another wet sump now that MRC is available on all Corvettes.

LT1 Z51

The time component is now a part of the OLM.

Which to me makes the OLM mostly useless. Because I feel a 12 month change is overkill. For a lightly used car with trips that are of medium length, a 24 month change interval is fine if you don't hit the mileage.

In the C6 it was easy to track this because the OLM didn't have the time component.

JerryU

^^^^
If after warranty is up and you want to change oil and filter every 2 years the timer is still a big help! When it says zero life left after year one, just zero it out like you changed oil (15 second task, and it’s not bugging you every time you start the car) and it will tell you again in one more year!

In my case I do my own oil changes so changing once per year with the Mobil $12 rebate/5 quart jug (two allowed) that is ~$2/quart and a fun 30 minute task! I also do a Ranger clutch fluid replacement at the same time.

LT1 Z51

Except I want to know when I hit the mileage limit. OLM was great for that. To tell you based (solely) on use, when to change your oil.

For me it's on use or at 24 months.

The new one takes time as a factor, which defats the purpose. Time while a component to oil breakdown is not something that is at all agreed upon by engineers. Where as the other stuff (short trips, high temps, abusive environments, lots of high RPM excursions) are generally accepted as being bad for oil.

So resetting the OLM is not really an option, because it eliminates all the good data I want to capture when I also get rid of the bad data (the time component).

Basically, GM had a VERY good system and ruined it by adding a time component. To me its **** poor engineering.

vettetwo

Keep in mind that GM recommends an oil change at least once every 12 months and if the owner does that, they pay for any repairs. If the owner thinks they know better and extends the interval beyond 12 months, GM may not pay for repairs. The OLM is simply a measurement of compliance with recommendations.

JerryU

^^^
The “once a year” minimum oil change requirement is what the Owner’s Manual for my C6 Vette said, quoting, “Your engine oil and filter must be changed at least once a year”

Believe my ‘93 Vette and 1988 Vette said something similar. This is not a new requirment.

No big deal either way, I put all my maintanence in the Owner’s Manual where there is a place to do that!

LT1 Z51

That is 100% a CYOA sentence.

For the record, the algorithm was probably changed because that's unenforceable. You can't deny coverage based on a time interval of changing oil unless the oil is proven to be bad and have caused the damage.

However, its more enforceable to deny coverage based on the OLM since it takes into account things that do say the oil is damaged.

Basically, GM used an algorithm to define what they say is bad oil and you can't use independent analysis to go against this. Under the old way you could say that it was good oil, have it analyzed and be proven right and in fact you could use the OLM against GM in its argument that it should deny you coverage for not changing it at the 12 month mark (because the OLM said it was still fine).

Legalities aside, what SHOULD bother all of you is now instead of providing a USEFUL algorithm GM has converted you to a SHEEP who now must change his oil every 12 months regardless of if its actually bad.

Posts like the one I quoted annoy me because they DON'T care that GM has made us SHEEP.

LT1 Z51

Don't use that word.

In no way shape or form is anything that is printed in GMs service manual a requirement. They are all RECOOMENDATIONS.

GM (and most companies) understand that the average consumer is ignorant (and afraid) and so they try to word things in such a way to scare you.

Nothing in your service manual is enforceable. Warranty coverage cannot be denied based on it. Only the cars onboard diagnostic systems can be used as well as proven analysis (for example like Blackstone Oil tests) to deny coverage.

Could a dealer try to deny it, could GM, sure, but if you fought it in court you'd win (unless you had incompetent counsel). I posted on here before the owners manual, the actual sentences do not say required. They use words like recommended, and may deny. They do not use words like required and will deny.

JerryU

^^^
First, the words I quoted are from the C6 Owner’s Manual NOT the Service Manual!

Second, funny I am in a 2 day meeting as a member of the Committee that has to approve the >50 documents produced by our Society for welding, Bridges,
Buildings, Airplanes, Tractors, Automobiles etc! As usual, we go though Should, Shall, Recommend etc in our codes! Turns out no word is really “safe” as attorneys and Warning Label “Experts” argue both ways in court! Juries have no idea and listen to whoever sounds the best! The main issue we cover is the need to be consistent in all our documents, which we occasionally are not!

I’m just saying, the once a year minimum oil change requirment is nothing new! It has been in the Owner’s Manual for years! Now off to another day of Codes and Stanards discussions!

LT1 Z51

Owner/Service/random GM document.

Irrelevant where, language is same.

Internets_Ninja

My OLM advises me to change the oil in my car around 6000 miles every time no matter how I drive it. I use my "B" tripometer to track the miles. So it works great for me and I'm sure about 99% of every other Corvette owner.

So I for one, do not share your subjective opinion of the OLM. If it's useless to you then don't follow it.

LT1 Z51

You must drive extremely consistent.

I've had the OLM in at least 6 GM cars (between my parents and myself). The C7 is the first one I've had issues with the way it works.

I'm betting I have more miles under GM's OLMs than most of you do. So you'll have to excuse me when I say it's your opinions who are invalid.

EDIT: The cars are 2004 Malibu, 2007 9-3, 2006 GTO, 2008 Corvette, 1998 Regal, 2001 Alero, 2000 Aurora, 2005 Envoy, 2006 9-3, 2008 VUE. My 1997 Grand Am may have even had it but I can't remember. Those 10 cars (maybe more depending on how many cars in the 90's had it) have over 400,000 miles combined. Pretty sure that's more than most of you.

vettetwo

No one's opinion is invalid. It may be different than yours, but that is what keeps forums lively. If forum rules were such that only opinions like the OP were allowed, forums would not be worth reading.