I would never go 15k to 25k between changes with a 2.7 Intrepid. The engine has inheirent oil flow problems. You want to keep the oil clean & prevent even the slightest bit of sludge buildup.

I change my Mobil1 every 7500 miles,but I been using synthetic oil since both cars were new, and they are still running great with over 220k miles.

If you have been using regular oil, I would start using synthetic and change the oil every 3000 miles to ensure the sludge is disapated. If you removed your oil Pan and manualy removed the sludge, maybe you can get away with 7500 mile oil changes.

Remember the the Interpid engine CAN NOT TOLERATE SLUDGE! It's oil circulating system is poor with small flow tubes/holes and you are puting the synthetic oil to it extreme design heat specifications. You want to keep the synthetic oil clean.