There are about 30,000 calories in a gallon (about 4 liters) of gasoline, which is enough to power a person for about 20 days, depending on your caloric intake. Human beings burn energy quite efficiently. In fact, the average person riding about 15 miles per hour (about 25 km/h) on a bike could do more than 900 miles per gallon (nearly 400 kpl) on a bike if they could refuel.
More energy facts:
Vegetable oil actually contains about the same number of calories as gasoline, so if the human body only needed fuel, not nutrients, it could fill up on a few gallons of vegetable oil a month and finish the month’s diet. .
On a chemical level, gasoline and vegetable oil are very similar. They both contain long chains of hydrogen and carbon, making it possible to convert vegetable oils for use in some cars.
Fuel efficiency in humans declines rapidly with accompanying speed and air resistance. For example, in the bicycle example, going 10 mph faster cuts the miles per gallon by about two-thirds.