My daily driver is a Renault Master, and my other half has a C5 hdi, at least we're flying the flag for French motoring, however economical or not it maybe
Regarding the "lowest mpg" suggestion, may i start this with an old Rover P5B, 3.5 V8 i used to own in the early 80's while working as a joiner in Newcastle, my round trip to work and back was around 8miles and it "drank" most of this per day, i was never in a financial position it fill it up, but estimated it did around 10 mpg,
Cheers for now Paul