If you prepay your fuel with Dollar, they are overcharging. For my mid-size cars, they are charging a flat $49.90. Most mid-size cars have either a 12 or 13 gallon tank. Based on that, they are charging $3.83 or more per gallon to prepay. Their prepay is consistently doing the same on all other sizes. Alamo charges a per gallon price based on current gas prices ($2.62). My mid-size will cost me $34.45 ($15 less).