Actually, the oil life monitoring system is very accurate, as long as:
It is reset at each oil change...
You use the correct oil (it is programmed for a particular oil spec, and if you use an inferior oil, it does not know this, use a better oil and it does not know this either; however, it will not cause any future problems)...
Depending on your driving habits, a 3K oil change is only good for the oil companies and their employees and stock holders (see note below). (Ever notice that all those so-called pros who recommend a 3K oil change all have their fingers in the oil industry?)
Just watch your OnStar readings (or purchase a Tech 2), and actually monitor the oil life percentage. In the colder months, it will reduce at a faster rate for miles driven, then it does in the warmer months; providing you are not driving in the Sahara.
Someone who does short drives in the winter, not allowing the oil to warm up, will have the light kick on a lot sooner, than someone who drives a decent warm up cycle, which allows the moisture in the engine to burn off. Oil improvements in the past 10 years has been amazing as well as the longevity of the oil additives used. GM, as well as all other mfgrs spent millions on research and testing of this system, and they did it to help their customers cut operating costs, while allowing for no damage to the internal components of the engine.
For those who disbelieve, my suggestion is before saying something does not work, obtain the proof.
I have my oil analyzed on all my vehicles on the second oil change. I ship off a sample to Blackstones, and they in turn send me a complete oil analysis, including the TBN. So far, on all my vehicles (including the Vette) that have an oil life monitoring system, the oil analysis indicated the oil was still healthy, didn't need changing, and was not high in any trace elements except for those used by the oil company, or those natural to that particular engine.
Example, on my '03 Vette, when the monitor indicated 20% life remaining, I would head up to the store, purchase my Mobil 1, then within a week or two (depending on driving) I would change the oil. My results from Blackstone's was usually 6 or 8 TBN, with high trace amounts of calcium (additive used by Mobil), and in the early years, high nickel (common on the LS1 engine). Average miles on the oil was in the 6-8000 mile range, with the low end during the cooler months, and the high end in the warmer months.
The only thing the system can not take into consideration is dirt entering the engine. If you are using a paper style air filter, and the box, as well as all the other intake areas are sealed properly, that is not a problem. If using a foam type filter, then I would recommend (my recommendation only) changing earlier, depending on where you have been driving. If only city roads, there should be no problem, if off-roading, dirt will be entering the engine. Foam filters are not good filters for filtering dirt. Many tests prove this, and that is one reason why I will never use one (that and dynos I have had performed proved no increase in HP.)
To sum it up, it is your engine, do what you want. However, to save money, to help reduce oil imports, go with the monitor. If you decide to change your oil every 3K, I personally thank you, since my retirement fund is primarily based on oil stocks, and the more oil you'll purchase, the sooner I might be able to retire. (Oh, and use XM too, that helps the retirement account too.)
