Really good point I was thinking about myself. Today I experienced noticeably quicker acceleration on my return trip I was taking than when I left. I took Route 7 from Leesburg from Winchester, which is a hilly stretch. Got about 34.5 mpg overall--but I'm really not driving to conserve fuel and have no qualms about stomping on it to pass somebody or to go uphill.

Anyway, the way there, the battery was about half charged almost the whole way, and the car did feel a little sluggish to me. On the way home, after I had been messing around with it showing my family, it was almost totally charged and felt noticeably quicker.

I can't see how it WOULDN'T affect test results.