I arrived at the Seattle Hilton National lobby counter last Sunday morning, to pick up my one-way compact to Boston. The clerk said they have just one compact- a 2012 Chevrolet Sonic sedan, ~20k mi, silver, and NV plates. The others were all full size cars. The garage seemed almost empty, with an odd Altima sprinkled in. To my surprise, the car was given from a neighborhood store with a full gas tank.
I asked the clerk if the Sonic is indeed a compact, or really a subcompact. He replied it is a compact. The keychain and window barcodes all said ECAR. Not that I really cared. At the time I booked, the rates for subcompacts and compacts were the same, and I was by myself anyway.
The gas mileage seemed decent, at least 33 mpg, especially once I-90 left the mountain west. Maybe this car was not as fuel efficient as some of the other small ones I've rented, but good enough.