My dealer tells me that Mopar is in the process of changing oil suppliers from Mobil to Pennzoil for it's Mopar MaxPro packaged engine oils. I've used Mopar Max or MaxPro since the '70s in my vehicles and want to continue so is Pennzoil as good as Mobil? My new Jeep Liberty calls for 5w20 which my dealer parts guy says in the Mopar MaxPro line is a Pennzoil synthetic blend. Is this a good quality oil for my new Liberty 3.7 V6?