The following article states that in the past, if a driver put Regular gas in a car that required Premium, the engine would start Knocking (pre-ignition) before the car even left the gas station. But that today, the car (or truck) has a computer that can compensate. Still, it is allowable to use Regular in an engine which is supposed to have Premium, ONLY if there is no Premium available.
The question of whether or not you can damage a car that asks for premium gas by using regular gas is one that never seems to die.
www.thedrive.com
Also, Premium fuel will not provide greater gas mileage ... unless you define "greater gas mileage" as NOT having the engine become broken.