[brucepick]

To take a completely different approach - Is it possible to measure fuel electronically on these diesels?? Maybe not easy, but might be easier than building calibrated fuel cells.

If you can set up something that creates a ground when the injector is firing then an MPGuino can measure fuel flow. That is, as long as the fuel pressure is consistent as it is in modern gasoline vehicles. If you don't measure speed electronically the MPGuino won't care - it will just keep toting up fuel qty until you zero it. You'd have to get miles from an odometer or GPS but it's really a separate issue.