1600 miles, you're talking like 4 fillups...probably nothing to worry about.
You also didn't state what kind of MPG you are seeing...note that is very subjective depending on driving conditions. The worst thing for mileage is idling...in that you're not moving but burning fuel=0 mpg. Stop and go is just as bad.
With that said, best guess your first run with the car you were averaging over 27 mpg, now you're averaging shy of 24 mpg based on usage of 16 gallons (minus reserve). Probably completely normal based on driving conditions.
You also didn't state what kind of MPG you are seeing...note that is very subjective depending on driving conditions. The worst thing for mileage is idling...in that you're not moving but burning fuel=0 mpg. Stop and go is just as bad.
With that said, best guess your first run with the car you were averaging over 27 mpg, now you're averaging shy of 24 mpg based on usage of 16 gallons (minus reserve). Probably completely normal based on driving conditions.