If you look at the top 10, as said earlier, small motor, standard transmission light weight and older vehicles. None of the drivetrains in the top 10 are available anymore (I might be wrong)..... That means you can buy an an inexpensive used car that will beat the ICE powered new cars! I also wonder why technology took a step backwards..............?
"If the engine ain't running it ain't using gas!"
Of course I'm going to suggest you add Tempo/Topaz to your list, but only the m/t versions! They'll deliver more than 30 mpg even without any high FE driving techniques.
And they have to be about the dirt-cheapest cars you can find these days. A couple hundred bucks usually does it.
I'd stay away from the newer Integras -- better to go with a Civic (lighter, trust me).
As for the Prizm: It's essentially a Corolla, but with a Geo/Chevy emblem on it, so it commands a lower price. They were made in the same factory in Calif. as an agreement with Toyota and GM. Today that agreement makes the Matrix/Vibe.
If you get the Tempo, look for Diesel, right Clench!
If you get a chance, find an "Intellichoice" Used-Car magazine at a bookstore to get a picture of Used vehicles, prices, and depreciation -- and as always, Consumer Reports Auto Edition for reliability.
edit: and I almost forgot: The VW Diesels require the changing of the Timing Belt at like every 60K miles, so that's a lot of work/expense
AND as for most of these cars that have "Valve Operlap", get it in writing that the Timing Belt was replaced or if it fails, the cylinders crash into the valves and the whole engine's screwed.
For inexpensive used fuel sipping cars it's hard to beat the Suzuki Swift/Geo Metro. The 3 cylinder 5 speed version is great if you don't mind it being a little low on power. Mine is the SOHC 4 cylinder 5 speed which has sufficient power to cruise at 80+, and very tall gearing. Driving normally on the hwy at 60 mph I can get 50 mpg. Around town it's about 40. (summer time temps). Here are a couple pics of the car.
FYI my old 3 cylinder 04 Geo 5 door on a trip to Alabama I drove 80+ in the rain at night no problem at that speed - when you start getting up to 90 then it tops out. Never drove so far so fast in my life - three tanks of gas in a day.