Originally Posted By: DdDd
I did 150k miles on that motor in the TJ using nothing fancier than M1 5w-30 changed every year or 10k miles, whichever came first.
Filter I used was one size up PH8 in fram I believe. The one that fits the old ford 5.0. It held more oil than the stocker and had more filter.
When the engine finally croaked it was a head gasket leak that did it in. Sudden coolant loss out the cylinders lol. When the mechanic was looking at it he was astounded how new the internals and hatching looked. No ridges or sludge.
Only goes to show, worry about oil until you're blue in the face. Any number of things can get you. Yes they had a defective head casting in those early 2000 models. Id check the stamping if I were you. Google the problems...
0331 head issue was solved by 2001 so not an issue for OP in his '05.
While M1 is a very good oil, I'll say again that it's well documented that M1 produces more than twice the iron wear in this engine.