I got a dose of low grade, high alcohol or bad gas after I paid for premium, my 8.1 liter dually ran so bad while towing the race trailer that the gas pedal was almost flat on the floor going home.
If it wants to ping, the computer takes away timing which kills horsepower. My race gas is leaded and oxygenated, or I would have helped it out with a shot of that. It isn't a flex fuel vehicle but doesn't seem to mind E10 gas.