they used an ice suit to keep the driver cool... and stopped often to get more ice.
Here's how they went 2507 miles on a full 48.6 gallon tank...
only one person in the car to reduce weight,
no air conditioning equipment,
aerodynamics of a 300mph car (looks like McLaren design from the front),
and a 70 mpg rating from a VW 1.9-liter turbo-diesel inline four-cylinder motor that is good for around 220 hp rwhp
Result? An average of 66.7 miles per gallon at an average speed of 67.6 mph, reaching a top speed of 91.1 mph and only consumed 37.6 gallons
Transmisson Audi 6 speed
3 gears from 3.5 to 1.3, then 3 overdrive gears taller than usual, at .87 to .56,
The final gear ratio is said to be 3.875
The stat page doesn't mention the gears between trans and tires
tires - Front: 245/40-18 Rear: 255/40-19
Car weight dry - 2100 pounds
Instead of only putting 10 gallons of fuel in at a time, they started in Florida with a full tank. I don't think that's a good idea, as a gallon of fuel is about 8 pounds, and every 10 gallons is most of a hundred pounds. Starting a cross country trip with a full tank is carrying an extra 360 pounds you don't need to and hurting your mileage for 90% of the trip.