I'm sure there are many opinions on this for sure. I run Castrol full synthetic 20W50 in my E46, which gets driven only about 4k-5k miles per year, it's a weekender, and I work from home so no daily commute. I change the oil twice a year. If it were a daily driver, I would change the oil every 6k-7k, based on my driving habits. If I were running a non-synthetic or blend, I would change it about every 4k-5k, unless you are really driving it hard (harsh conditions), then I would do it a bit more often. I would think these are very conservative intervals and you could probably go longer, but this is just one guys opinion.
Edit: Short duration trips, like daily commutes of only 15 to 20 minutes, or those short trips to the store, are harder on your oil and parts than long road miles. If your daily drive consists of lots of very short trips, then I would change my oil a bit more on the low end of the range. If you do a lot of road driving, then push it on out there and don't worry about it as much. One of the reasons I change my oil twice a year, is because my car sits a lot. I've read somewhere that moisture and other contaminants can collect in the oil and cause corrosion and friction. Long drives, where your oil tends to heat up, will help eliminate any moisture build up in your oil. At least this is what I've read on the subject. Driving in dirty, dusty conditions is also considered a harsh environment and would lead me to err on more frequent oil changes and using only high quality filters. I've had good success with engines over the years using this philosophy. Oil is a critical part of good engine maintenance any way you slice it. Use good quality oil and filters, adopt a habit of regular changes, and rest easy.
Last edited by TexHog188; 12-11-2013 at 12:52 PM.