Check out my patent US#7677208. Ford was working with DOT and U of Michigan as well as Parker Hannefin about 10 years ago on a hydraulic hybrid. I though that was very interesting and highly efficient. I think their 80 MPG 3800 pound mule used a 1.9 turbodiesel. They also came close to a HH F150, think it was called the Tonka but it faded away.
What a shame.
http://www.epa.gov/otaq/technology/r...n-vehicles.htm
Oh yeah almost forgot. Welcome to EM.
regards
mech