How often do you really need to change the oil in your car?

Factual Questions
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The quality of American cars now surpasses the quality of European cars, so I’m guessing that differences in engines isn’t the answer.

Basically, it’s all a big scam to get American drivers to change their oil more often than necessary. FWIW, my Saturn has a “Change Oil Soon” light that comes on about every 6000 miles. (It’s actually a little less than that; the car’s computer starts with 6000 and lowers the interval based on how you drive.) I use the Change Oil Soon light as my guide to when I pull into the local Oil Joint.

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My basis for this conclusion lies in the standards for engine oil performance introduced by the European-market automaker’s association, ACEA.
The performance standards for an ACEA A3 oil are head and shoulders above the most recent and most demanding of the performance standards that American auto-makers reccomend, which is the API’s SL rating.
Cites on this?
Truthfully, I tried to pull some up, but the proxy server in the office is running out of RAM, and all the PDFs I tried to open failed to make it through. I’ll try from home.

Side Notes:

  1. Some years of Corvette do spec fully synthetic 5W30, so the Corvette does have to be taken out of this particular argument.
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Finally, I must amend my last post. While it is my belief that it is likely the case, I will not be producing citation on this subject matter. I can procure abundant disucssions of related issues, but I am no longer wholly certain that the questioned assertion is correct. It is, however, true that the ACEA specifications are harsh compared to the API specifications. In fact, ACEA A3 in particular seems to demand a synthetic, which no API spec has ever done.