3k oil chages came around in the 40's. Oils have advanced since then, and filters have both been added and improved. (Although if you own an older VW Beetle, you might not have an oil filter unless you put in an aftermarket kit.)

In Consumer Reports 4.5 million mile test, they saw no reason to go with quicker oil changes and synthetic oil. That being said, I use 5k changes with synthetic oil and Puralator pureOne filters, since the guys that tear them apart on the web and post pictures all say they're a good deal, and universally hate the cheap Fram filters. (Expensive Fram's do a little better).


Do your own investigation, YMMV, and here's the consumer's report article. It also talks about additives:
http://www.xs11.com/stories/croil96.shtml

There's another Consumers Reports reprint on the web--I want this job! Driving a car without oil to see if the "oil miracles" you see on TV work. Of course, the answer is no.
http://xcelplus.com/industry_info/consumerreport.htm