1. Changing your oil every 3,000 miles
There are two different points here. First—it’s very easy to change your own oil, and paying someone else to do it is seriously frowned upon in some circles. Second—there is absolutely no reason to change your oil at 3,000 mile intervals. That was the standard in the 1960s, but with today’s synthetic oils, you can get away with five times that.
While manufacturers recommend 7,500 to 10,000 miles, that’s mostly to soothe the minds of people used to 3,000 mile changes. I’ve spoken with some of the engineers responsible for these recommendations—you can do 15,000 or even 18,000 miles before you’re pushing the limits. Still not sure? Have your own oil tested. You'll be amazed at how clean it is.