Yep, as I have documented before 100-300 mpg has been  possible for decades with "regular" on "regular" gas.
 Quoted: "Here's a car that was 20 years old at the time of  the contest that was the project of a couple of guys in a garage," he said. "You  can't tell me we can't do better than this with cars today." Read about Shells 376 MPG Opel here