Your sample size is too low, and accelleration is less efficient. A slightly different test that would give completely different results would be to reach cruising speed at 60mpg, reset the meter there, then change to 30mpg and compare. I'll bet your "average" will instead be closer to 50 rather than 40 in that situation. As the sample size (trip miles) gets larger, the mpg swings in either direction will get smaller.

Someday I might even beat that wascally kenny!

No whammies... no whammies... no whammies...