What is the record for longest distance of a production vehicle using the factory gas tank?

[savefuel]

Yeah, that's well above the Guinness World Record but the vehicle has been modified and was no longer a 'factory car'. Also: Driving a constant 57 km/h / 35.4 mph on the German Autobahn is illegal and could not be done today, 41 years later. But it clearly shows that TDI's are efficient (and were so a loooong time ago) and that a low curb weight combined with low roll resistance (aerodynamics are a lesser factor at that speed)are the key to success ...

[cRiPpLe_rOoStEr]

fewer emissions-related devices also allowed for a greater overall efficiency, even with those old-school indirect-injection engines.