Chrysler recommends that unleaded fuel only with a minimum octane rating of at least 87 be used in your vehicle. Since your vehicle is equipped with a catalytic converter, the use of unleaded gasoline is required in order to meet all emission regulations, and to prevent damage to the converter which would occur if leaded gas was to be used.
Fuels of the same octane rating have varying anti-knock qualities. Thus, if your engine knocks or pings, try switching brands of gasoline before trying a more expansive higher octane fuel.
Your engine's fuel requirements can change with time, due to carbon buildup which changes the compression ratio. If switching brands or grades of gas doesn't work, check the ignition timing. If it is necessary to retard timing from specifications, don't change it more than about 4°. Retarded timing will reduce power output and fuel mileage and increase engine temperature.