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.
Gasoline Eco Cruze has a 15.6 gallon tank, not the EPA supposed 12.6 gallon tank with sensor that cuts it off at 12.6 gallons. Continued slow gasoline filling will use the full 15.6 gallon capacity. Therefore, the highway range of gasoline Eco Cruze is within 50miles of diesel Eco Cruze.