Methinks this is dry humor, at it's driest. And the "Thank you Green Hybrid" at the end is in reference to the fact that, in spite of those horrible conditions that in previous cases had ruined his MPG, yet by employing those GreenHybrid tips, he was able to perform a Herculean effort and maintain his MPG at 48.4.

Or, maybe I'm just stupid and that's not it at all. But I'm sticking with the dry humor explanation.