Well I changed my oil at 5000 miles and the oil was dirtier than Christina Aguilera on the "Dirty" video. The oil had some consistency left, but it was very dark, kind of burnt like. So my uneducated guestimate for you guys is to do your own mid interval changes at around 5000 miles. I believe our engines are worth a lot more than that. My assumption is the maintenace program changes the oil at around 15000 miles so when the car reaches out of warranty territory it will be ready for engine problems. It may be paranoid, but everything falls a design.

Send it away to have it analyzed to confirm your results... I've found that longer drain intervals are just fine for the car. I regularly ran my oil out to 9000 miles (even with track time) and analysis said that it was fine. After 9000 miles tho, the car did ask for an oil change so I changed it and the filter.

I did the old skool test. Stuck index finger in dirty oil and taste it. Not very pleasant!!! :D I kid. I already threw the oil down the street drain, no not really, I took it to recycle. I will next time. Where can I do that oil analysis?

http://www.blackstone-labs.com/