The GF bought a new 2004 Jeep Wrangler with the 4.0 I6. I had the oil changed at 1k, and 3k with Castrol GTX 10w30. At 6k I put in Amsoil S3k 5w30 HDD just because I had alot of it laying around. She drives the Jeep 55 miles each way to work and back so the oil gets plenty warm. I plan on running synthetic with extended drains but would like to know what you guys think would be best in this engine. S2k 0w30? S3k 5w30 HDD? At the rate she puts miles on this thing I think I'll have a few UOA's a year, which is O.K. by me . Of course all the other lubes will get swapped with synthetic.