Good question...
I didn't think of that - this goes back to a previous discussion we had on the subject.
We could state the reason it is considered fuel efficient or what it is best used for. For example, the Metro is a great city commuter, but not fantastic on the highway and you definitely aren't going to tow a holiday trailer with it...an F350 diesel is actually pretty efficient in that regard.
Just list what YOU feel is an FE car and I will organize it into something that makes sense.