same truck i had posted about a few times before, my buddies 2011 1500 chevy with the 4.8 vortec, which now has 66k miles. I noticed in the owners manual that it says to use dexos, but also says if dexos isnt available to use an API approved oil. Last oil change, which I did at 64,800, i used Valvoline maxlife 5W30 and a Fram ultra. I change the oil every 5k, so i realized using synthetic is a waste. So would Maxlife or Pennzoil Conventional 5w30 and a wix or TG filter be more suited for 5k ocis? My buddy drives the truck VERY easy.