There is no set oil change interval - it is determined by the driving conditions and the condition of the engine. The older service intervals were just a ballpark figure - for most conditions, those mileage figures were perfectly valid. Once you add in some stop and go traffic, extended idling, and/or heavy engine loads - then shortening the interval is recommended. Most service schedules have a \"normal\" conditions guideline and one for \"severe service\" conditions.
With the formulations of modern conventional motor oil - 3K miles is excessively short for most people. Only way to tell for sure is it send in a used motor oil sampled to be chemically tested. Some cars can run longer on an oil change, some like shorter changes.
My current cars - I generally run a 7500-8000 mile oil change interval (synthetic motor oil). I have tested and run the oil out as long as 18K miles (synthetic) for an interval - the oil additive pachage was pretty much spent at that point, but still offered good protection for the engine.
3000 mile interval is becoming less and less desireable - some still stick with it, and the oil companies are all for that, some are starting to stretch them out to 5000 mile intervals or more. Only way to find out where you stand is to test your motor oil. Good example is this lab - http://www.blackstone-labs.com/
- I use them for my UOAs. Runs about $22 a test, less if you buy testing in bulk. Normally I test once a year - just to see how things are.
Check out bobistheoilguy forums (http://www.bobistheoilguy.com
) and carbible (http://www.carbibles.com/engineoil_bible.html
) for additional information. Lots of good info in there - just have to wade through some of the sales pitches and self-preaching that occurs there, but good info nonetheless.
2002 Corolla S, Silverstream, 1.8L 1ZZ-FE (VVT-i)
2003 Matrix XRS, Cosmic Blue, 1.8L 2ZZ-GE (VVTL-i) - RIP
2009 Matrix XRS, Blue Streak, 2.4L 2AZ-FE (VVT-i)