Looks like I'm going to be purchasing a high mileage (150k) 90s Jeep Cherokee for Daughter to drive. Just wondering what oil most of the Jeep owners have used with good success. These engines seem to be pretty bullet proof, so I'm a guessing a 10w30 Dino in the summer, 5w30 in the winter. I was thinking either Pennzoil HM 10w30 or Valvoline HM. Also, are most of these 6 quart fills? Thanks.