In the trunk he found documentation that the Fiat formerly owned by NASCAR founder Bill France had been used by Shell scientists for their annual fuel economy competition that continues to this day as the Shell Eco-Marathon. This year's winner was a streamliner that achieved 1,902 mpg.
In its day the 500 was stripped to the bare essentials, including ditching the reverse gear, radiator, fan and water pump and limiting the top speed to 16mph. It did manage to achieve 244mpg in 1969. Thanks to its history, instead of being parted out, the Fiat will now be restored to its 1969 condition.
[Source: Montgomery Advisor via Hugg, thanks to Linton for the tip]