Whether you go by the Normal or Severe conditions schedule, the owner's manual and service manual BOTH specify oil and filter changes together. Normal conditions specify 7500-mile/12 mo. change intervals, while Severe conditions specify 3750-mile/6 mo. change intervals. You can find places in the service manual that allow Normal service filter change at 15,000 miles or 12 mo., but DON'T short-change your engine on either oil or filter changes -- do 'em together. If you pay this much for a vehicle, it doesn't make sense to skimp on maintenance -- ever.