Opinions on oil life...

2007 Cobalt, 37xxx miles, 4 cylinder. Running Mobil 1. Its now, according to the oil change sticker, got 4000 miles on this oil and filter. The DIC says 67% oil life left.
About 98% of my driving is hiway, with speeds above 60 mph, the other 2% is city. No stop and go driving. I'm averaging 34.3 MPG, monthly average, and its an 80 mile round trip to work, five days a week.. So whats your opinion on when to change oil? 5000 miles, or when the DIC says its time? At this rate if I go by the DIC, I could have close to 10,000 on this oil before the computer says its time to change it. The oil is still fairly clear, not dark and dirty looking. What say you?
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With normal dino oil, most car makers say 7500 miles so using a good synthetic, 10,000 is not out of the question. I'd go a minimum of 7500 miles and probably closer to 90% used up on the DIC. Unless you live where it is 115 degrees in the summer or -25 in the winter.
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Ed Pawlowski wrote:
i think we live near each other. did you go to SCSU?
peter
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No, I went to Temple many years ago. I'm in the ne corner of CT
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Ed Pawlowski wrote:

peter
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wrote:

Who are you changing it for? Warranty purposes? If so, follow the book, or you risk loosing your warranty. Yourself? Personally, I'd say follow the DIC, but there is a 'better' way:
You can send a small sample of the oil to an oil analysis lab, for a small fee they'll check the oil, tell you what's happening with your engine, and how it is doing. They will also recommend any additives that may be needed.
But...
The cost of the lab, plus the additives if needed, may in fact be more than doing the more frequent oil changes. (This system is used mostly in big trucks where instead of 5 quarts of oil, you're talking as much as 5 to 10 gallons of oil, a major cost difference!
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Very true.
Some of the labs represented in a round robin report some time ago got considerably different results on they analyses, as well. But lets assume that the results you get from your lab are accurate.
Another factor is the interpretation of the results.. There are several ways you might interpret unexpected data, like high silicon content in the oil. Antifreeze? Bad air filter? Injudicious use of silicone sealants? ??
And last, if they detect something potentially damaging, what are you going to do? Rebuild the engine? Or change the oil. ( To what level of confidence and importance would you rate the analysis, is really the base question)
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Personally, I own a 2001 Monte Carlo LS, which uses the same Oil Life Monitor to determine when is the best time to change the oil. My opinion of this system so far is good. Twice now I have waited for the Service Oil indicator before I went ahead and changed it. Now, about 85% of my driving is highway, usually over 100 kms daily. The other 15% is mostly rural driving, and every now and then, a bit of city driving thrown in. This car has close to 180,000 kms, 3.4L, and so far, has not used any oil between changes, nor is it very dirty when I change it.
Now when I first bought the car a year ago, I didn't know when the oil had been changed, but it was very clean and the oil filter looked new. Like you, I was a bit skeptical as to letting the oil monitor decide for me, but gave it a chance. So I left it and decided I would wait, and finally around 8000 kms, it lit up. I changed the oil very soon afterwards and reset the system. The second time around was very near the same mileage, under the same driving conditions. I live in Nova Scotia, where the temperature can be -30c one day, and +20c the next, and the first oil change was indeed, a seasonal change. I think it was around November when it was changed. The car had been purchased in June.
I did alot of research on this system that GM had developed, and apparently, it looks as though they have spent alot of time and money to develop this system. In my opinion, it is accurate, based on the results I have seen thus far with my own GM car. It pretty much does the same job as sending the oil into a lab technician to have them analyze it, except it does this constantly by computer/electronics, inside the car, while you are driving. Another reasoning factor was that most websites explained that todays engines are far more advanced than those of 20 years ago, when the norm was to change at least every 5000 kms. It certainly doesn't hurt to change the oil around 5k, but you are not getting the most out of your oil by doing so. So, personally, I believe there is no reason not to use the monitor, unless you are old fashioned and like keeping track of your oil changes yourself. And there is no problem with that, only that this monitor was designed to save you from doing so.
Just my 2 cents Sharky
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I know GM spent a lot to develop this system. It is not a "monitor" as such, in that it does not check any of the parameters of the oil. As you mention, these systems function by mathematical calculations only.
If anyone wants to depend upon them, there is certainly a basis of scientific development that would support it.
Basically, many of us have our own opinion about how important oil changes really are. In the same sense, we have our minds made up about what brands of oils and filters are acceptable, how long we want to run our engine oil, and whether or not synthetic or dino will do what we expect.
It is an argument which will never be solved. That is why I usually say, "It is your car, do what you want to do".
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That's right - no analysis. Mostly just counting revs, not miles/kms, and monitoring outside temperature. No allowance for synthetic as far as I can tell.
I change the oil in my 2009 Uplander 3.9 the weekend following when the computer tells me to.
I have 17,500 miles and I have changed it twice with about 60+ % left till the next change.
Why waste oil?
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There was an article about how GM/Honda see 12.5K mile oil life as possible, I guess under highway conditions. But these monitors can light up as low as 3000 miles??
Most of these monitors use algorithms, but I believe only Mercedes tries to measure viscosity or something like that. But with synthetics and oil monitor, Mercedes can go up to 20K mile intervals.
But once a year or up to 7,500 miles is probably safer.

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On Mon, 22 Jun 2009 23:09:31 -0500, Deke fired up the etcha-a-sketch and scratched out:

I just change mine every 5000 or so miles.
Works fine.
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I can remember changing oil every 3000 miles. ( this was back in the 60's, 70's 80's ) It always came out looking like tar !
My 2002 BUICK Century was my first; "Change oil when the light comes on"
Even at 5000 mile intervals, the oil often looked as clean as the day it went in....
Who knows ?? Maybe at some future date oil will be a permanent ( sealed ) part of the engine.
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I am of the old school, who changes oil and filter frequently. It works for me, is not too expensive.
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On Wed, 24 Jun 2009 18:55:18 -0500, HLS fired up the etcha-a-sketch and scratched out:

Like I often say - cheap insurance.
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