I am the world's top authority on oil changes. Call me Mr. Motor Oil.
Here's the bottom line on oil changes: The 3,000 mile interval is a myth that the oil companies and oil change places have perpetuated.
It certainly wouldn't HURT to change your oil every 100 miles, but even the most thick-headed can see that this would be overkill.
I change my oil and filter in my Japanese car every 4,000 miles and always have---and this is lots of city driving, and it is STILL overkill. The car has over 180,000 miles on it, has never required anything more than basic maintenance (no engine work) and is still going like new. I've always used Castrol GTX dino, but many quality brands will do.
In my BMW, I change my oil about every 8,500 miles (if I followed the "computer" it would be more like every 12,000 miles or so), and use Mobile 1 Synthetic, which is overkill, but I do it anyway. I just enjoy changing my oil I guess. But, you hard heads, do the environment a favor and stop the unecessary oil changing.