Yes i have some idea's for the truck to improve the economy.
It is a Ford econovan maxi tho its just a rebadged Mazda E2000 it has the Mazda 2l FE petrol engine.
JohnAh i believe that the orbital engine was bought out by a big Auto maker and is still being worked on.
I also came across a modern retro fit for a fuel injection system for two stroke motors but is a throttle body type so not likely to be much better then a carby system. If you could fit a direct injection system like the one you mentioned on the marine v6 to our old 2t motors that would be great.
Must also remember that 4 stroke engines still consume a small amout of oil tho it is minimal then there is dealing with the used oil and oil filters that are left over from 4 stroke motors
Cheers Jamie