I have a 2002 Ford Escape. The owners manual says to change the oil every 6 months except in "extreme conditions" - my extreme condition is I do make a lot of short trips as I now live in a small town. 3 miles to the store, etc. I have only 82K miles on it and have had it since it was new. How often do I really need to get the oil changed? It takes me a long time to get to 5k miles so I'm not sure how all that works. I've been doing it every 4 or 5 months since I moved here. Thanks!