Originally Posted by mpwallin
I live in rural pa. Not much city driving but not highway at all. Mostly 2 lane clipping at 60,down hill one way and up back. 2010 with 4.7 got 17.5-18.5 consistently without trying. I realize the break in thing but how much does that really change. Would different octane help enough to justify price diff, never tried it in any other vehicle? Any help is appreciated.
Mine changed a good bit after the first 500 miles (for the better), and again around 3k seemed like things settled in a bit more after service. Then again, I was looking for power not efficiency, but 16-18 is my norm now with a mix of light urban driving. (89 octane)