The classic way to convey the error that exists in a measurement is a formula that shows the obtained measurement (X) as a sum of a true score plus some error. One version of this formula is: X = T + e. With this formula in mind, obtaining more precise measures depends on reducing error.
  Mega is the prefix meaning one million, therefore there are one million (1,000,000) gallons in a mega gallon.
According to the US Government's Energy Information Administration, the United States consumes about 400 million gallons (1.51 billion litres) of gasoline every day. That figure equates to about 20 million barrels of oil every day. 2.