Those days are long gone. The cars and the oil aren't what Dad dealt with. I remember plugs, points, and condenser every 2K miles, and if you didn't you would be walking. Plug wires and distributor and cap at 5K. You might or might not be walking if you skipped this one. My dad made a decent living off people skipping these procedures. The auto came with a book, it will have change intervals. If it is under 10 years old, it probably has an oil life indicator, that requires no effort on your part. I was able to adjust, but many aren't. I grew up a bit of a gear head as well. Not to worry, it's your money to waste and you don't seem to be one of those ecoterrorist sorts.