91 Octane in a 340?

if there is only one nozzle at the gas pump your probably getting around one gallon of whatever the previous customers octane choice was. if he bought 89 octane before you show up to fill up with 94 octane your gonna get 1 gallon of 89 octane with ethanol. so if your serious you can sit around and watch what fuel grade is purchased at the pumps by previous customers before you pull up to fill up.