Once we learn something it is hard to unlearn it. This is especially true if we learned it in our youth. To this end, ever since I began driving in the early 1980's, I was told to change the oil in my car every 3000 miles. While I haven't been a stickler about the rule, I have tried to follow it closely. Imagine my surprise then when I "unlearned" today that oil should be changed somewhere between 5,000 and 7,500 miles. (For precise details, I refer you to this article.)
Old habits die hard but if you want to save some money and do what's right for the environment, unlearn and start changing your oil less frequently. Of course, you could–as the photo above suggests–also accomplish both goals by driving less and biking more.