I looked through the
EcoModder Fleet list - EcoModder.com of gasoline vehicles, and the highest ranked automatic I found was #143 - chuckm's
2002 Toyota Corolla.
There may have been a higher ranked automatic, I got tired of seeing Metro after Metro, so I may have skipped a few, but if that is the highest, you're not too far away. That 90-day MPG is 45.3, so you're only a few MPG's away from being the best meeting your criteria. At least, as far as Ecomodder is concerned.