Had a few straight 6s over the years...the Jeep 4.0 was pretty durable, put 170k on my '00 GC with that engine..leaked oil a bit past 100k and had many electrical issues, but the engine itself was fine. Also had a BMW w/ the S52 3.2 straight 6, great engine, and drove a Mercedes W124 300CE quite a bit w/ the 3.0 6...