According to the service tech that gave a talk at my dealer's new owners' clinic, there are very few places that don't come under the "extreme conditions" category. If you drive in hot (above 90) or cold temperatures, or any mixture of such. If you drive in city traffic, or particularly hilly or mountainous roads. if you do lots of short trips. Obviously, if you hot rod a lot. All these qualify for more frequent changes. They generally recommend that if you are in doubt, then use the extreme conditions schedule and change oil every 3750 miles. That's what I plan to do.