Corvett4Ever

Hello everyone,

This is oil change related question. I know there are hundred of thousand of threads here talking about oil change related topics and most of them are related to Z51 500 mile oil change. My question is not about that. I have already done my 500 mile oil change 4 months before and I'm good with that.

The question is: As I have done my 500 mile oil change on 12/22/2014 (4 months before) oil life monitor in DIC is currently displaying 66% oil life. But the service sticker on the windshield says that

Next service due date is 04/21/2015
Oil life 20%

Now I'm confused because as per the service sticker next service date is tomorrow. But the current oil life is 66%. So what should take the precedence? What is the general rule of thumb? Service date? mileage? or Oil life monitor?

My car has only completed 2700 miles so far and that means after 500 mile oil change, I have driven 2200 miles only. When I check the user manual, it says oil change required every 7500 miles only.
Why manual only mentioned about 7500 miles.



Note: I did search about this topic in this forum and in Google, but couldn't find any similar topic. Sorry If this topic has been discussed before and If I have missed that.


Thanks!!

Steve_R

You get four oil & filter changes in the first two years, in addition to the one at 500 miles, any time and mileage you want them. After that use the oil life monitor, not a sticker somebody slapped on.

EcoBrick Bob

I think a reasonable person would say to change oil at least once a year or every 7,500 mi with Mobil 1. However, since you get 4 more changes, I would have it changed every 6 months, finishing up with your last free change just before the 2 year mark. That's what I'm going to do anyway. My C5 had less than 24K at nearly 7 years of ownership, so obviously had to change oil annually.

Cruiter

I'm doing same thing. Just had my 3rd change last week at 18240 and will get my last (free) one late Sept or early Oct just before the two year anniversary. Using Hendricks and getting Mobil 1.

Gr8ful

I change my oil at 800 and at 2400 (1 year). Every 4k from now on. I will not be using my free dealer oil changes because I don't want the least trained person at the dealership to even come near my Stingray.
I wish I could give them away to someone and I bet the dealer won't just give the oil and filters to me either.
It's just not worth saving $50 on my $70k machine plus I like getting to know the car personally.
My $.02 worth.

fdxpilot

Call the service department that put the sticker in your car. Tell them their sticker says it's time for an oil change, and "I assume this is one of my free oil changes, with Mobil 1?" If they say yes, go,for it. If not, you have until Dec (1 year) or till the OLMS says change your oil.

Corvett4Ever

Thanks for the replies everyone!!

So what is the generic rule? Oil life monitor, or Mileage, or time ? or which ever come first ?

I know we can use all the 4 free oil changes at any time we want, And most of the people don't drive their car much so they can use all 4 oil changes exactly within 2 years. but If we drive the car too much, then we have to do the oil change more frequently right? For example let say you drive the car 40,000 per year (just an example) So your oil life goes very fast within a year. though it is only 1 year you may have to change the oil 3 times if oil life monitor goes to 20% for three times.

In my case oil life is 66% and mileage is 2700. So technically I have enough oil life. but time has reached.

Anyway I will call my dealer and check this and see what they are going to say.

Thanks!!

meyerweb

First thing, read the manual. It doesn't say to change the oil at 7500 miles, and it says nothing about 6 months. It says to change it when the oil change indicator says to change it.


What is says is to check the oil LEVEL at 7500 miles, and change it IF the oil life system tells you to:

You only need to change it when the oil life system tells you to.

If you drive a lot of miles, the DIC will tell you change the oil sooner than if you drive fewer miles. You still don't need to change it until the car tells you to. The only reason the sticker tells you to change more often is to make the dealer more money, not because the car needs it. You don't even really need to worry about the 1 year timeline, because the oil life monitor will notify you when you hit the year.

The only reason to change your oil more frequently than the DIC tells you to is because you get 5 free changes in the first 2 years, so you might as well change the oil every 6 months to take advantage of those free changes. After two years, only change when the DIC tells you to.

If your dealer tells you that you need to change it at 6 months, find another dealer, because they're lying to you. Read post #3 in this thread for all you need to know about the oil life monitor:

https://www.corvetteforum.com/forums...indicator.html

Corvett4Ever

Thank you very much!!
That is the straight answer I was looking for. You sum up all the points

C7Joy

I am in the same camp with most of what has already been said. In a nutshell, get your free changes, then give precedence to the oil life monitor becuase it takes time into account.

JerryU

After my first early oil change (I do my own) I use the GM oil monitor, which for the C7 also uses time so if other factors don't say to change sooner (like miles, oil not getting hot enough because of short trips etc etc, it will say change in 1 year. IMO it is conservative and a good way to define when to change, unless you’re tracking etc. Recently found this document posted if you want to understand how sophisticated that oil change algorithm is, read the following. It is a very complex algorithm and developed over years of work. This was taken from an older post about the GM Oil Life Monitoring System and was posted on BobIsTheOilGuy:

“One thing I can touch on and clear up.....the GM oil life monitor operation and my statement that ZDP (or ZDDP as you tend to call it here...most of the API literature just sticks to ZDP so I tend to use that) depletion is the basis for oil deterioration.
My spelling is poor but ZDP stands for zinc dialkyldithiophosphate which , as it sounds, is an anti-wear compound comprised of zinc and phosphorus.
ZDP is dispersed in the oil so as to be at a potential wear site if a surface asperity happens to break thru the oil film thickness causing the dreaded metal-to-metal contact. A molecule of ZDP must be present at that moment to prevent microwelding at the contact site which will cause material transfer, scuffing, scoring, wear and catostrophic failure. The concentration of ZDP in the oil will determine if there is ZDP present to work it's magic. The greater the concentration...the more likely a molecule of ZDP will be there...and vice versa.
By nature, ZDP is sacrifical. As ZDP is "used up" at a wear site to prevent micorwelding the concentration of ZDP decreases.... So...if you measure the ZDP concentration in engine oil in a running engine it will decrease at linear rate based on engine revolutions. Any given engine has a certain number of high potential wear areas where metal-to-metal contact could occur due to reduced film thickness and/or surface asperities....areas such as rubbing element cam followers, distributor gears, rocker arm pivots, push rod tips, etc...... The more of these areas the more ZDP depletion. The more often these features come in contact the greater the ZDP depletion. That is why, generally speaking, ZDP concentration in the oil, for any given engine, will decrease at a fairly linear rate when plotted versus cummulative engine revolutions. The more times it turns the more contact the more chance for wear the greater the depletion. This is as much of a fact as I could quote ever and is really not speculation or anything. It is proven beyond a shadow of a doubt in many studies. That is why it is ONE of the basis for determining oil life remaining and why it is THE basic premis of the GM oil life algorithm. It is only ONE of the things that determines oil life...but it is the one thing that can be tied to engine operation in a linear fashion and estimated very accurately by accumulating engine revolutions via a counter.
The GM engine oil life monitor counts engine revolutions and accumulates the number for the basis of the oil life calculation. It then adds deterioration factors for operating temperature, start up temperature, soak times, ambient, coolant temperature, etc... There are a LOT of factors that "adjust" or affect the slope of the deterioration but the fundamental deterioration is traced back to the ZDP depletion that is inescapable with engine revolutions. The specific rate of ZDP depletion is readily measurable for any given engine so that is the fundamental item that is first calibrated for the oil life algorithm to tailor it specifically to that engine.
You would obviously like to get the oil out of the engine before the ZDP concentration gets so low that it is ineffective at being at the right place at the right time and preventing engine wear so that becomes the long term limit on oil life for that application.
The other things that determine oil life such a acid build up, oxidation, petane insuluables such as silicon from dust/dirt, carbon or soot build up from the EGR in blowby, water contamination, fuel contamination, etc.... are all modeled by the multipliers or deterioration factors that "adjust" the immediate slope of the line defined by the engine revolution counter as those items can be modeled in other ways and accounted for in the immediate slope of the ZDP depletion line.
The algorithm was developed over the course of many years by several lubrication experts at GM Fuels and Lubes, spearheaded by Doctor Shirley Schwartz who holds the patents (with GM) for the algorithm and the oil life montitor. I had the luck of working directly with Dr. Schwartz when the idea of the oil life monitor first progressed from the theoretical/lab stage to real world testing/development/validation. There were fleets of cars operated under all conditions that deteriorate the oil life for any and every reason and , thru oil sampling and detailed analysis of the oil condition, the algorithm was developed, fine tuned and validated to be the most accurate way invented yet to recommend an oil change interval by. As just one example, I have seen cars driven side-by-side on trips, one towing a trailer and one not, for instance, to prove the effectiveness of the oil life monitor in deteriorating the oil at a faster rate just because of the higher load, higher average RPM, higher temps, etc...and it works flawlessly.
The oil life monitor is so effective because: it is customized for that specific vehicle/engine, it takes everything into account that deteriorates the oil, it is ALWAYS working so as to take into account THAT INDIVIDUALS driving schedule, and it tailors the oil change to that schedule and predicts, on an ongoing basis, the oil life remaining so that that specific individual can plan an oil change accordingly. No other system can do this that effectively.
One thing is that I know personally from years of testing and thousands of oil analysis that the oil life algorithm works. There is simply no argument to the contrary. If you don't believe me, fine, but, trust me, it works. It is accurate because it has been calibrated for each specific engine it is installed on and there is considerable testing and validation of the oil life monitor on that specific application.
Oil condition sensors in some BMW and Mercedes products are useful, also. They have their limitations, though, as they can be blind to some contaminates and can, themselves, be contaminated by certain markers or constituents of certain engine oils. Oil condition sensors can only react to the specific oil at that moment and they add complexity, cost and another potential item to fail. One other beauty of the GM oil life monitor is that it is all software and does not add any mechanical complexity, mass, wiring or potential failure mechanism.
There is considerable safety factor in the GM oil life monitor. Typically, I would say, there is a 2:1 safety factor in the slope of the ZDP depletion curve....in other words, zero percent oil life per the ZDP depletion is not zero ZDP but twice the concentration of ZDP considered critical for THAT engine to operate under all conditions reliably with no wear. This is always a subject of discussion as to just how low do you want the ZDP to get before the oil is "worn out" if this is the deciding factor for oil life. We would tend to be on the conservative side. If the oil life is counting down on a slope that would recommend a 10K change interval then there is probably 20K oil life before the ZDP is catostrophically depleted....not that you would want to go there...but reason why many people are successful in running those change intervals.
There are entire SAE papers written on the GM oil life monitor and one could write a book on it so it is hard to touch on all aspects of it in a single post. Hopefully we hit the high spots. Realize that a GREAT deal of time, work and energy went into developing the oil life monitor and it has received acclaim from engineering organizations, petroleum organizations, environmental groups all across the board. It is not some widget invented in a week and tacked onto the car.”