I drive my RAM about 2k mi/yr. (at 9 mpg I prefer to use it only for hauling/4X4 use/etc vs. normal commuting). Oil gets changed annually. I've used M1 10W-30 since it was new but it seems a waist to change out all 7 qts at only 2kmi. What dino oils do well in a V10?? I'm wondering if the fleet oils like Longlife or Delo are too thick at 15W-40? Would Chevron Supreme 10W-30 be a good choice or should I just stick with M1?