Try Royal Purple. First oil change in my 2009 SRT8 Challenger picked up 1+ MPG over the factory fill of Mobil 1. Shop around for it; CarQuest here has it on sale $7.49 qt for a case sale. Also think about a catch can for the PCV line-these motors, (5.7 & 6.1) create alot of oil vapor and without the catch can it goes in the intake.