I remember reading somewhere online at a site dedicated to information about oil types, manufacturers, filters, etc, where they sorted through the crap (FRAM filters for example) as well as the myths about oil (changing every 3000 miles), and it talks about how just because oil is dark in color, does not mean that it is "bad" or "used up" or whatever. Sure, that nice golden color is great, but heat alone will change the color of the oil, even if it isn't breaking down.
With that said, I keep an eye on my mileage, I know how much highway vs. city driving I've done, and I have been doing pretty well with oil changes (100% quality synthetic oil and a good filter) about every 8,000 miles (mostly highway). The oil is dark, but not as black as non-synthetic at about 2000 miles, and the oil life gauge is at about 15% left. Oil changes are relatively cheap, so why risk it. For some people who do all city driving, that may be at 40% on the life meter, or people using regular, non-synthetic oil it may be something different.
If you are worried about the cost, just drop 50 cents into a jar every day that you drive the car and you should have more than enough money to cover the costs when you need ot change the oil if you do it yourself...
