First tank after replacing my HV battery and first tank though my Prius in general. How'd I do?

Good work!!!!

My experience: once you get a used Gen2 sorted out, it is one of the greatest, most efficient and delightful cars ever.

 

A newbie's progress through the stages of hybrid ownership is always good to watch.

In addition to the improvements you taken so far with the car, a big factor is climate. Low a/c and heat use during moderate weather means more energy is applied to moving the car down the road and not the sub-systems. In PA, you should see mileage decrease during summer with a rise again next fall before plummeting in the winter.

Once you get the car sorted, look into "pulse and glide" and other techniques in this sub-forum that others have discovered pays big dividends in fuel economy.

 

Well you don't REALLY know what your efficiency IS having only the number of gallons used.
You also need the actual miles driven to do the math.
And the number of gallons used on a single fillup might not be accurate either.