Step one: Buy a used 2005 Prius. This will cost about $19k.
2005 Toyota Prius with Carpool Stickers/Navigation System
Step two: Convert to PHEV (plug in electric version.) This will run about $6k.
How to Get a Plug-In Hybrid
Step three: Profit! 160 MPG on a $0.50 charge. That's 1,500 miles on a tank.
YouTube - 171mpg in Prius Plug-in Hybrid Electric (PHEV)