Oh Man! I thought we were finally going to get a 600 mile tank! Had 595 on the ODO... Showing 54.9 mpg... about 8 miles to the nearest gas station... ADD FUEL has been flashing for maybe 50 miles... Just as a precaution, I put the gas can used for the lawn mower on the floor of the rear seat. My house is at the bottom of about a 150 foot hill to the south. It's tough to go up that SOB every morning, but a lot of fun to glide down... all the way into our neighborhood and into the driveway... on the trip home. Up the hill I go... oh oh... strange loss of "power" weird engine revving... RED TRIANGLE OF DOOM!!! All dashboard warning lights ON !!! "Cap'n, I don't think the warp drive can take much more." DANG IT! I get to the top of the hill and roll into the elementary school on battery power. With two PINK battery bars showing. Oh well. I don't know how much gas I poured into the Prius, maybe a half gallon to 1 gallon. No more for sure. But I managed 595 miles. When I started the car I still had Triangle of Death and "Check Engine" icon as well as "Add Fuel." The gas pump "auto shut off" at 9.8 gallons. I gently added almost another gallon to bring it to about 10.5 gallons -sorry, I left the paperwork in the car. All warning lights were off following the fill up and I put about 200 miles on the car since then without issue @ 54.5 MPG. So there is really no telling what I started out at - fuel-wise. Maybe I had the full 11.9 gallons, maybe I didn't fill it up all the way like some of you do. Anyways, an interesting story - at least to me.