I just took a trip from LA to SF and only got 36 mpg. My speed was 72-75 on the 5 fwy.

7/2/17 276.00 7.602 36.31 2.499
7/2/17 232.00 6.423 36.12 2.919
6/30/17 220.00 6.620 33.23 3.399
6/30/17 97.00 2.500 38.80 2.799

What gives?