A hybrid that gets 53 MPG is great, but that's nothing compared to a VW that can pull 235 MPG, or a car built by Turkish students that averages 621 MPG. These cars may not exactly be the most fun to drive, but they are certainly the most eco-friendly. Whether you're an eco-warrior, or a bio-fuel curious gearhead, be sure to check out all of these mega MPG concept cars below. Who knows? One day we may be seeing and driving them on a regular basis.

The Volkswagen XL1 is built for MPGs, not speed. This green concept pairs a 1.0-liter engine to an electric motor, returning a stunning 235 MPG. That's the good news; the bad news is that the performance numbers are appalling. The XL1 has a top speed of 75 miles per hour and a 0 to 60 time anywhere between 11 and 32 seconds.

Only the most diehard eco-warriors would commute to work in the MAELSTROM (Mobile Aerodynamic Light-Weight Super-Mileage Tri-Wheeled Road Monster). The ridiculously named vehicle was designed by students at the University of New Haven and looks strikingly similar to a baby carriage. The MAELSTROM is slightly more expensive than a baby carriage, with a price tag of $25,000. It also gets better gas mileage, averaging 500 MPG.

A group of Turkish university students at Sakarya University built a 240-pound hydrogen car that returns a stunning 621 MPG. The compact cruiser cost $170,000 to build and was designed for the 2009 Global Green Challenge in the Australian Outback. Take that, America.

Loremo AG showed off the diesel-powered LS and GT at Geneva 2006. These two cars had pitifully small engines (20hp 2-cylinder and 50hp 3-cylinder respectively) and outrageously low price tags. Both cars returned well over 100 MPG, and both were less than $20,000. Anyone know what ever happened to Loremo AG?