What type of gas should I fill up my car with an engine of variable-venturi?

they only difference between regular and premium is the octane ... octane is a measurement for the knock residence so higher performance engines like superchargers turbos or engines with really high compression ratio need higher octane or the engine will have pre ignition .. so if you have any of the above then run premium if you don't then just use regular i don't get why people thing premium is better for your car its only better if you have a engine the can utilize it ... i really don't get the lead thing all gas these days are lead free the leaded gas in the 70s and earlier was to lube the valves i believe or somthing along those lines not postive on that