Im not trying to hinder your experiment, but it would give you more results to analyze if you drove longer distances between diagnostic/parts changes.
I'm following this thread closely because I'm a bit of a mpg nut too.
I get 53 on my street bike and average 17 half city, half freeway in...
just introducing my self to all of you. Recently I've gotten this itch to get a Dart or Valiant, don't really have the time to devote to it right now (first career status job doing 12 hour days) so I'll just live vicariously through you by reading about the trials and tribulations here on the...
you aren't going far enough to really be accurate. at that level if you had gotten in only .3 gallons more your numbers would be way off what they are now.
you need to get into the 10 gallon or so fill-up range.