To find the range, you would need to:
1. Identify the specific engine and transmission: Was it a 2.4L 4-cylinder, a 2.0L turbocharged 4-cylinder, or a 3.6L V6? This significantly impacts fuel economy.
2. Find the EPA estimated MPG: Look up the EPA fuel economy estimates for that specific 2013 Buick Regal configuration online (e.g., fueleconomy.gov or Edmunds.com). You'll find separate city and highway MPG figures.
3. Determine the fuel tank capacity: This is typically around 18 gallons for the 2013 Regal, but it's best to verify this in your owner's manual or online specifications.
4. Calculate the range: Multiply the city MPG by the fuel tank capacity to get the city range, and do the same for the highway MPG to get the highway range.
Without knowing the specific engine and transmission, I cannot provide a definitive answer.