I still think there must be something f'ed up in that car to get mileage that low. I was getting 12 and 13 mpg when I had some ignition problems along with a bad cat. Since its been fixed, I almost always get 18. If I drive like an absolute hammer, 17. I betcha there is some gremlin at work in there.

Good luck, hope you find the problem and are able to keep/enjoy this wonderful car.

 

No wonder you're getting 13 MPG--you're going 90 on the freeway and getting pulled over. Go away.
https://www.rx8club.com/rx-8-discussion-3/cops-profiling-rx-115775/