Crazy three wheel cars
 

These 3 wheeled cars are built for performance, but if they had a smaller engine and improved areodynamics they would have really good fuel economy. They weight around 1,000 pounds so that helps alot.

https://www.go-t-rex.com/

https://www.vwvortex.com/artman/publish/volkswagen_news/article_1647.shtml

https://www.sub3wheeler.com/index.php

https://www.vigillante.com/vigillante1.htm

https://www.rqriley.com/tri-mag.html

(you can order plans on this page. I bet you can find them for free if you look on the internet for a while)

https://www.arielatom.com/ariel/site.php

a very light 4 wheeler)

Those are really cool. I
 

Those are really cool.

I sort of want to build my own car now :)

Although it is still in
 

Although it is still in development (they are presently constructing the prototype), the Aptera diesel-electric hybrid by Accelerated Composites (https://www.acceleratedcomposites.com/) looks promising with its 330 mpg projected mileage and its cd of 0.055.