I Recently drove my 91 Deville 4.9 from Chattanooga to Atlanta and back (about 120 mile trip each way) and found my highway mileage to be most excelent. i got between 29-30 MPG. But in town, and in traffic, i got about 15 MPG. I wasnt happy. If only i could switch between my Nissan and my Caddy, id have the perfect setup for mpg and comfort.