Throw away the sticker. They just want your money. Oil will last MORE than 12 months but you're supposed to change the oil at 12 months and that is when you get to "0". If you get to 0 before the 12 months, then it was a mileage thing that required the change and not a calendar.


Elmer

 

my oil gets changed every 10000, regardless


4 Corvettes ,during a 20 year span, with a total of about 140000 on them together
they never used any oil, either

 

Answering question of what happens to oil after a year:

I recalled a comment made by a fellow who has forgotten more about engine oils than I know-not my area of expertise! He was an oil refinery engineer and posts periodically on the forum.

However as you'll see from his last statement I'm quoting from another Thread, he believes oil analysis will not be a good indicator of when to change, here are his statements:
"There are three main villains with regard to oil life: sludge, acidity, and oxidation. Sludge is mainly what turns the oil black, and is mainly condensed hydrocarbons from piston blowby. Assuming your rings are in decent shape, you haven’t disconnected your PCV system, and you don’t leave your oil in for ridiculous intervals, this should not be much of a problem.

The other two issues (acidity and oxidation) are related, because the carboxylic acids that can eventually form contain oxygen atoms, so initial oxidation is a necessary step along the route to acid formation. Oils have both anti-oxidants and pH stabilizers to prevent this from happening, but eventually those become depleted. The main feature of extended life oil is having more of those additives so that you can drive more miles before they are depleted. But reverse logic does not apply. Having an excess of those additives if you change your oil often does not give you any added protection. So it would not make sense, for example, to use extended life oil and then change it every 3000 miles, figuring that would give you added protection. Incidentally, while oxidation and carboxylic acids may cause the oil to discolor a bit toward brown, they will not turn it black, so a non-black dipstick does not necessarily equate to ok oil.

The problem in answering the original question (how often to change oil) is that so many factors influence how rapidly the degradation from sludge, acidity, and oxidation occur. How well are your rings and seals performing? How hard do you drive? Are there any odd environmental factors like unusually dusty, hot, or pulling heavy loads? And the biggest of all, how often do you shut the car down before it is thoroughly hot, recognizing that damage from that practice gets exponentially worse if you have several semi-warm shutdowns in a row before getting it thoroughly hot. Semi-warm shutdown is important because that leads to condensed water vapor getting in the oil, which seriously aggravates oxidation and acid formation. Is time itself a problem, meaning change it after X months or years regardless of mileage? If you don‘t have any of the above oil stress factors, time itself isn’t an issue until at least 1 or probably more like 2 years. Similarly, if you don’t have any of those stress factors, there’s no reason not to run the oil life monitor all the way down.

I know I haven’t given you an exact answer, but that’s because no exact answer exists. The answer is everybody’s favorite, namely, “it depends." Hopefully, the above gives you at least a sense of what it depends on.

Used oil analyses are pretty much worthless. Yes, if you are about to have a catastrophic engine failure, they will show elevated metals. Yes, if you’ve left your oil in way beyond anti-oxidant and pH stabilizer depletion they will show low pH and high oxidation products. But your engine is toast way before such signs show up. For anything resembling a normal engine, there is far more random noise variation from sample to sample than there is true, underlying effect. If used oil analyses were reliable and useful, no oil companies would do the very expensive engine tests needed to assess wear properly. But they do such testing, which conclusively shows how useless used engine oil tests are."

Why I change my street rod engine oil every year with few miles.

The 8.2 Liter ZZ502 Chevy crate motor in my street rod also states change oil a minimum every year. The car mostly is driven to local shows and I am careful to avoid starting it up if I don't drive at least 20 miles to get the oil hot. It has large forged pistons that have large clearances when cold. The Holley 850 double pumper is set rich, especially at idle (I use an oxygen sensor to monitor the air/fuel ratio.) It has lots of blowby on startup, you can hear the pistons rattle for a few minutes! Water is a main product of combustion so I know it is passing the rings. Also when just parked the humidity changes day to night in the garage cause condensate on cylinder walls. Changing oil one a year is cheap insurance, IMO

 

 

 

Three? My window sticker says two.

 

I don't think you can go wrong by following the OLM. I do. But in my case it leads to the other extreme, less miles between changes.

 

As I understand the meaning of the wording, the 500 mile oil change is not a general maintenance requirement it's for dry sumps only because of a "possible" oil foam issue that "may" cause oil foam because of silicon from curing seals depleting the antifoam agents in the factory oil fill. That foam "may" burp with the air from the dry sump tank to the incoming air intake tube and drip on the ground from the air filter.

Note, my " " are the words GM used in their bulletin on the subject. Dry sumps get that free as well.

From forum posts since I got my September 2013 built Z51 C7 it appears to me that oil dripping from the air filter is more likely caused by a dealer overfilling! Has been reported right after a dealer 500 mile change by some folks! I change my own oil and since that GM bulletin and recommendation did not come out for 13 months after I got my car I changed oil at 1500 miles as a precaution not knowing anything about foaming! Did not have one drop of oil in my air intake, but then I never overfilled!

 

Mine is a GS. All dry sump models (GS, Z51 and Z06) get a 3rd free change at 500 miles. Base models get only 2 changes.

 

 

I've gone 10k miles, with no problems whatsoever, between Mobil1 changes with our two cars ('07 and '10 Lexus) for years, and it usually takes at least two years to hit that mileage. Currently the cars have over 80k and 60k respectively. In fact, the '10 actually calls for 10k changes. However, I'll adhere to the Corvette's OLM until the warranty is up, then every 10k will be the norm.

 

I've got to disagree with this. I've used Blackstone for several cars over their lifetimes, and have learned of several problems that otherwise would have continued. Once Blackstone warned me about high silicon content in my C5's oil, which I traced to the PCV crossover on the back of the engine that had decomposed and broken open.

Another time, again on my C5, I was running the OLM down to 0%, and wear metals started trending higher. As a result I started changing oil at 25% left, and the wear metals cleaned up.

Oil analysis is just a tool, but it's certainly not worthless.

Have a good one,
Mike

 

^^^^
Wasn't my comment but do respect this fellows opinion. As I read what he said it was an oil analysis cannot tell you if the oil is fine it can only pick up problems. His point was a quality oil is usually changed before it picks up metal wear.

You obviously found issues even when you were changing per the GM recommendation.

I know that some truck fleets use it all the time since they operate their engines for 200,000+ miles and are looking for specific wear parts/materials.

 

They are just being extra cautious, but I know for a fact you can go longer than this, as I have been doing 2 year oil change intervals with my C6 (with Mobil 1 5w30) and I get the oil analyzed at that point and the reports show it could go even longer.

 

^^^

Probably correct, the GM algorithm is reported to be conservative by a fellow who worked with the PhD that developed it with lots of testing and data. However also may depend on the specific engine and driving conditions. As VetteDrmr stated he found an oil analysis showed a possible issue a few times at 0 OLM and he has altered his procedure to change when the OLM says 25%.

As the "oil expert" who occasionally posts on the Forum says, paraphrasing: "An analysis will not show some of the reasons for changing and when finding metals the oil should have been changed sooner!"

Everyone can do as they wish but I think following the GM recommendation (that has been in place for all 5 of my Vettes: i.e. change at minimum once a year) and now that the C7 uses a calendar and says to change in 12 mounts minimum, it is a good idea. As noted the Chevy crate motor in my street rod also says change a minimum of once a year and I consider it cheap insurance.

Just my $0.02. Perhaps only worth that!

 

This is good to keep in mind. While we can legitimately discuss when to change the oil, in the overall scheme of things it's not very expensive, especially if you DIY.

Have a good one,
Mike

 

I suppose since I’m getting indirectly quoted, I should chime in. Odds I will convince an oil analysis fan to stop doing it are low, so I’m really addressing someone considering whether to do it. My point has always been that in a healthy engine, there is way too much noise (ie, random variation) in such analyses to make them useful as an indicator of when to change oil or to compare performance of different brands of oil. If you could do that, nobody would need to do engine testing with subsequent tear-down and inspection to develop better oils. You’d just run them a bit and analyze the oil, which would be vastly cheaper than the tear-down and inspection route. Since neither car makers nor oil companies rely on the cheaper, oil analysis approach, then despite claims of analysis proponents, it seems to me that you can be highly confident that it is neither reliable nor useful for comparing oils, or telling useful things about reasonably healthy oil in a reasonably healthy engine.

Oil analysis is only useful as an indicator (by sharp and substantial increase in contained metals) of an upcoming major failure, and even then, the dual questions are how likely that is to occur and how much you would gain by knowing of such a thing a bit before it actually happens. Unless you have a very high mileage car or use it very severely (ie, racing), odds you are going to have a failure that you could see in advance from oil analysis are very low. And even in the unlikely event you catch something like a bearing problem in advance, it’s not going to turn a zillion dollar repair into a 50 cent repair. Virtually any such repair would require pulling and at least partially tearing down the engine, so it’s not going to be cheap. A bit cheaper than if you let the part go to failure, where it might take other parts with it? Possibly. But if I combine the low odds that I’ll ever have a problem that oil analysis would flag with the low odds that knowledge would save dramatically on repair cost, it doesn’t seem like a winning proposition to me. I concede in advance that the forum contains a few anecdotal stories that contradict the prior sentence, but there are not enough of those to change my conclusion.

 

^^ I have known a few people who did regular oil analysis that found trace amounts of glycol in the oil, and traced it to a leaky head gasket. In those cases, if left untreated the repair bill would be been in the thousands instead of being in the hundreds.

In my own experience, I saw high fuel levels (7%!) in the oil in my 2006 Civic and traced that to a leaky injector. I ran a couple of bottles of Gumout Regane through the tank and on the next oil analysis the fuel level was back down to zero again.

I do agree that engine teardown is the only true way to gauge engine wear, but oil analysis is still very useful and a lot of people use it to keep track of the health of their engine and to help determine the proper oil change intervals for their driving situations. It has worked for me for the past 15 or so years and I only pay $20 per kit so it's not terribly expensive. The lab is just a five minute drive from my work, so I simply drop off the sample right there and often get the results back within 48 hours.

I will say this about oil analysis, it has most certainly paid for itself over the years. If I had just continued with my previous habit of continuing to change my synthetic oil every 5 or 6000km, it would have cost me a fortune, compared to doing oil analysis at $20 each time, and seeing that I can most certainly go much longer between changes. I was changing my oil a few times a year, now on my wife's car and my Civic I only do it once a year and on my C6 I do it every two.

 

Thanks, didn't want to put your name in as "I was just paraphrasing and taking clips from your posted comments." Don't want to misrepresent the "teachers thoughts!"

 

I’m not trying to talk you or anyone else out of it. Different people have different ways of evaluating such things as risk and cost/benefit. I was simply expressing my opinion for what it’s worth to those who might be sitting on the fence. Your advice to those same people is the opposite. That’s fine, it would be a boring world if everyone agreed on everything all the time. But we do agree on some things. Though I’d argue that an oil analysis shouldn’t be required to believe it, I’d certainly agree that changing synthetic oil every 5000-6000 km (3000-4000 miles) is way overly conservative.

No problem. Just figured I’d re-state a few key points for emphasis.