Ah, I noted you were considering a Prius at the start of the post, but I think I was tripped up by "internal combustion engine" and "miles per gallon", thinking you were referring to a group of non-hybrid gas-only vehicles as candidates for your car of choice. I know there are several out there that get around 40mpg, but I didn't think they were as good as 50mpg yet, at least for a car that can seat 4 adults and pass all US safety and emissions requirements.