"Millas por galon" is a Spanish phrase that translates to "miles per gallon" in English. Word by word, "millas" translates to "miles," "por" translates to "per," and "galon" translates to "gallon."
Miles per gallon is a measurement that determines the fuel economy of a vehicle. A vehicle with a high number of miles per gallon is fuel efficient. The most fuel-efficient midsize car of 2015, excluding electric cars, is the Toyota Prius Hybrid, with 50 miles per gallon.
Cars that run on electricity cannot measure fuel efficiency in miles per gallon. FuelEconomy.gov uses a conversion factor to translate the fuel economy of electric cars into a miles-per-gallon equivalent.