Well, I guess I will dive in. I changed my oil last time at 5K and it still looked quite clean. I am going to 6K on the next one. Admittedly, my type of service is very easy on oil. I commute 150 miles a day round trip and it is almost all highway. Lately, I have been mixing four quarts of regular oil (10W40, whatever is on special) and one quart of Walmart house brand synthetic, which they seem to have stopped carrying for some reason. Probably so I will have to buy the higher priced, heavily advertised name brands. I think most people can go at least 4K and 5K would probably be fine. Changing very often doesn't hurt anything, it just uses up more oil and money. Oil "breaking in" should go into the oil mythology hall of fame along with "can't mix synthetic and conventional" and "can't mix brands". The major impediment in pushing drain intervals for me is psychological: I start to get real antsy to change after about 4500 miles. Lubricants are very high quality these days. Also, cleaner fuels such as low sulphur diesel and unleaded gas help greatly to extend intervals by reducing oil contamination.