To convert gallons to liters, you can multiply the number of gallons by the conversion factor (approximately 3.8 liters per gallon).
Julie bought 15.4 gallons of gasoline, so you can calculate the total liters as follows:
\[ 15.4 \text{ gallons} \times 3.8 \text{ liters/gallon} = 58.52 \text{ liters} \]
Thus, Julie purchased approximately 58.52 liters of gasoline.