I have a '03 Dorango with 29000 miles. I have changed my oil every 3000 miles with Castrol. I just changed jobs and I now have a take home vehicle and I don't drive the Durange very much. Before I hade my take home vehicle, I would put about 75 miles a day going back and forth to work. Now my Durango sits in my garage and sometimes I go a month without driving it. I wanted to know if I should go to synthetic oil or stick with conventional oil? I don't want to have to change my oir every 3 months because sometimes I only drive it once a month.