I have a "hard headed" relative with a 2006 Jeep I-6 4.0L Rubicon who recently had the engine rebuilt at 96,000 miles (he's the 2nd owner) . Moving on , he is very lax about oil change intervals so I put him into a Fram Ultra oil filter with Valvoline 10W30 synthetic oil . At 7,500 miles of suburban driving I stsrted advising him it's time to think about an oil change . His reply was he was going to wait until 10,000 miles - then do an oil change . Needless to say we are in disagreement over the OCI - especially after spending good money to have the engine rebuilt ! At any rate, because he insists on a 10K mile OCI I'm thinking of either moving him into Rotella T6 5W 40 OR Mobil 1 10W30 extended life while still keeping the Fram Ultra oil filter ... Which oil would do better in a jeep 4.0L I-6 if you are pushing the limit to a 10K OCI ?