Premium fuel in a stock 5.7 is nothing but a waste of money, it adds no extra horse power or torque. My 2019 fifth gen 1500 Laramie with 5.7, 392 gears and 4x4 calls for 89 octain or 87 octain. I've been using 89 until recently when I switched to 87 since fuel prices have gone crazy. I just returned from a 1200 mile trip pulling my 18 foot car hauler with a 5200 pound vehicle loaded on it and averaged 11.5 mpg with cruse control set on 68 mph. I have pulled this same trailer and vehicle on other occasions when I was using 89 octain fuel and there was no difference in fuel mileage. I don't think I will go back to 89 octain because the truck preformed great on 87 I see no reason to waste money. Every 10-k miles I run a can of seafoam fuel conditioner and cleaner in the tank, don't know if it is worth the trouble but I don't believe it hurts, I now have over 48-k on the truck with no issues of any kind since it was purchased, the oil is changed every 5-k .