I found this topic interesting. My range reads at 320 when I fill up but I don't usually make it to 300. I ran it all the down until the warning light was on and the gauage read empty and all it took was 14 gallons. And that was with topping it off. This is an ES330. I took the car in for its 1000 mile service today and asked them to check the gas gauge. They wanted to just explain the issue of leaving a reserve of 4.5 gallons away but finally agreed to do some checking and let me know. Having found this thread, I know now that something is amiss with my gas guage calibration or something.
Harry