EVRose

But where does it say the oil is "worn out" and the car knows how much time has passed between changes?

Vet Interested

Changing oil, transmission fluid, differential oil, whatever....it is in the Owner's Manual. Open it. You will be amazed what is in there.

Bruze

My late father told me a LONG time ago that oil doesn't ever really wear out; it just gets contaminated.

C6_Racer_X

I meant later C6's.

As for warranty, if the oil fails and causes engine problems (indicated by an analysis of a sample of the oil pulled from the engine), GM could certainly deny a warranty if you can't offer some proof that it was changed. Keeping receipts if you have a shop or $tealership doing the oil changes would suffice. If you do things yourself, then records of the purchase of oil and filters, and a log book or some kind of record of when and what the mileage was at the oil change. The better your records are, the less problem you'll have.

If it's synthetic oil, one year is the service life. Or 12,000 to 15,000 miles for Mobil One, unless the OLM system says less. The OLM usage is based on operating temps, loads, RPM's and other factors. The harder you drive, the quicker you use up the oil.

Oh, and for "conventional oils," without an OLM system, it's 3,000 to 4,500 miles or 3 months tops between oil changes.

The issue is that some of the additives decay and/or evaporate over time, and once you've opened the oil bottle, the clock starts on that. Also, with very low mileage, there's often periods when the thing sets for may days, and daytime temperature cycles and humidity put a lot of condensation into the oil. Water in the oil combines with impurities and combustion by products ("blow-by") and forms acids that can damage the engine internals.

zzjakect

Welker1

Mobile 1; Change when DIC indicates 25% or one year from last change, which ever comes first.

HOXXOH

THE ANNUAL OIL CHANGE EXPLAINED
The "once a year" thing has been in owner's manuals for about 60 years. Back when engines lacked oil filters the change interval was generally every 1000 miles, unless you needed to switch viscosity to suit seasons. With the advent of partial flow filters the change interval stepped up to 90 days or 3000 miles. and the 3000 mile part stayed there for decades. When full flow filters came on the market in the early 50's and warranties increased from 90 days pre-war to 12 months, manufacturers stated oil changes were due every 3000 miles or one year, whichever came first. The reasoning behind the 1 year interval, was that it was far easier to remember annual events like birthdays and major purchases, such as a car. Even though warranties increased to 2yr/24K miles in the '60's, the 1 year part remained to be a protection to the manufacturer. It has continued to be tied to the warranty requirements to the present.

The OLM is a far more accurate indicator than mileage or time, since the algorithm ties together all the factors that deplete the additives. The basic oil itself will last much longer, but once the first of the additives is gone, the wear factor increases.
You can use up the additives quickly by having the engine at high speeds, under loads (as in hills or acceleration), and high heat, or short trips that never get the oil hot. Conversely, light loads at low engine speeds for long distances will slow the additive depletion rate.

The OLM follows the same general pattern you would expect where fuel economy is concerned. Drive it hard and the tank goes dry quickly. Drive it steady in high gear and the tank lasts for many miles.

C6 Snowboarder

I change it when it needs to be changed.. and use mobile 1 - I think that is what is recommended in the service manual . read it somewhere... maybe a Camaro or BMW service manual somewhere.. Oh wait a minute of course. a Service manual for a Corvette? do they exist where owners can find this **** out on their own? by god now that would be a hell u va an idea -- Corvette to come with a service manual. Why haven't thy done this? Camaro, Mustang and BMW do this.

ruxvette

Me, too...but I change the filter every other month.



I carry a couple spare rolls in the cubby for that unexpected ooops.

Matthewstorm

Ha, thanks. Way TMI.

Matthewstorm

I have an '08 I bought in Oct.

owc6

I hate to be the breaker of bad news, but no C6 is "calendar aware."

The entire C6 run only takes into account engine run time, and what is happening whilst the engine is running. It has no idea how long since the last time the engine was fired up.

This "calendar awareness" did not start unit the C7 generation.

LMB-Z

Sometime between 5 & 10% on the OLM, or every year, whichever happens first. Not that is really needs it, but just as a precaution. Mobile 1 5w30 and a Fram filter probably.

OkieBikerDude

That's my M.O. as well. I use the high-mileage Mobil 1 as it has additives that were standard several years ago but have been removed from regular synthetic oil as being harmful to the environment if burned. One of the additives in the high mileage oil helps keep seals softer which is very important in vehicles that don't see a lot of use. Just my opinion, not trying to stir up anybody. OBD

LDB

If you just want the bottom line answer, skip this and the next paragraph and go to the third one. If you want to know a bit about why, read all paragraphs. There are a few minor misconceptions in this thread, but nothing seriously off. The two big enemies of oil life are oxidation and acid. Extended life oils have more antioxidants and pH stabilizers to fight those issues. Oxidation is almost entirely time related. Acids have a time component, but can be aggravated by poor ring condition or frequent short trips without getting the oil hot. The reason rings and short trips matter to acid is that water is required to form acids, and the source of water is almost entirely piston blowby, not moisture in the air. Exhaust gas is about 25%w water vapor because all of the hydrogen atoms in gas end up as water vapor after burning. When the engine and oil are cold, some of the water vapor in the piston blowby condenses into liquid water and can participate in acid formation. Getting the oil hot evaporates the liquid water and thus breaks down the acids.

With the advent of ever-better oil filter, ring, and additive technology, sludge is not much of a problem anymore unless your rings are seriously shot, giving heavy blowby. The only other issue that sometimes matters is the VI improver additive. That’s what’s used to give oil wider viscosity spread between W and plain number. So for example, 5W30 is 25 spread. Full synthetics have a natural spread of about 25, so 5W30 full synthetic does not need VI improver, but 0W40 does. Dino oil’s natural spread is around zero, and synthetic blends are around 10, so they do need VI improver even for 5W30. If the VI improver degrades, you can lose viscosity on the high number, so for example, a 0W40 full synthetic could degrade to 0W25, or a 5W30 dino oil could degrade all the way to 5W5. Reason for the degradation is that the VI improver molecules look sort of like an octopus. When cold, the tentacles wrap around the body so they flow easily like a ball, but when hot, the tentacles unwrap and extend, thus interfering with flow and increasing viscosity. They degrade by the arms breaking off, at which point, there is nothing to extend and increase the viscosity.

Bottom line is that if you use 5W30 full synthetic, don’t have shot rings, and don’t take frequent short trips, there’s absolutely zero oil-related risk to going a year or 10,000 miles between changes. With the added antioxidants and pH stabilizers of an extended life oil, you could do two years or 20,000 miles without real risk, although for warranty purposes, you might get in trouble. Brand of 5W30 full synthetic oil is not critical to those statements. Just like differences among top tier brands of gas are small, so are differences among the full synthetics. Claiming that one is dramatically better than another basis some test or property is just advertising-inspired silliness. Shades of gray differences? Sure. Dramatically better/worse? Nope.

cadyshac

Mobil 1 every 5k or annually whichever comes first. Managed to get 313,000 miles on a Trailblazer like that and woman I sold it to put another 60k on it before she sold it so I think I will stick to that routine.

Turbo6TA

And this is my dilemma ... I use 5W-30 Mobil 1 oil and an ACDelco UPF48R oil filter in my 2011 GS that now has 17,000 miles on it since I purchased the car new.

1. The last time I changed the oil was exactly 1 year + 1 month ago.

2. The car has 2,200 miles on it since that last oil change.

3. The OLM now shows 70% oil life remaining.

I feel that even though it's been a year since the last oil change, I would be throwing money away changing this fully synthetic oil that has only 2,200 miles on it (along with an OLM showing 70% life remaining).

But, it's been a year nonetheless ...

I just am having a hard time believing that the synthetic oil in my engine is in fact IN NEED of changing ? ?

LDB

If your car is still in warranty, that’s a separate issue. But if it’s not, I’d only ask one question. Which of the following two reasons best describes why you don’t drive many miles per year? Choice 1, you don’t drive it very often, but when you do drive it, you usually go far enough to get the oil temp up to at least 160 or 170 (coolant temp doesn’t matter, only oil temp counts). Choice 2, many, if not most of your trips are short, such as using it regularly for a short commute to work or running a nearby errand (coolant temp may be hot, but engine is frequently shut down with oil temp still below 160). If choice 1 is more nearly correct, I agree that there’s no oil-related reason (as opposed to warranty coverage reason) you can’t go 2 years. But if choice 2 is more nearly correct, due to acid concerns, I’d go ahead and change it after a year, despite the low mileage.

Turbo6TA

LDB .....

Good point

Ramets

I'm surprised Amsoil hasn't been mentioned more. I've used it for years in many cars & motorcycles with great results.