Diesel engine swaps for mpg?
 

My ls1 porsche is slowly coming along but in the meantime I'd really like to find a true ecomodder car. I would love to run a diesel engine in a small car. What is a very small diesel engine offered in the US and what could it go in easily? Could I find a cheaper Audi TDI engine and swap it into an older lighter audi?

I would love for the car to be a hatch and have enough room to throw a transmission or engine block inside. Worst case scenario I could always get a small trailer and a bike rack.

As of now I have an older 1999 dodge caravan that I'd love to trade for the car and engine. I think I might be a little optimistic but maybe I can work something out.