The EPA sticker in the 2003-2004 SSR (5.3L engine) and the 2005 SSR (6.0L engine) stated only 20 MPG (6-Speed manual) and 19 MPG (4 speed automatic) on the highway. I'm able to get 20.5 on the highway with my 05 SSR (automatic).
On my 05 SSR, my DIC MPG is usually about 0.5 to 0.7 MPG too low when I calculate the MPG manually. Interesting. The DIC will report 19.8 MPG and after filling the tank I'll calculate a MPG of 20.5 (and yes that's doing the math correctly)
When i picked up my new buggy I had 120 miles to home, florida turnpike. I did 60 and got 25.2mpg (reset everything before leaving dealer). I just came back from disney world doing 75-80 (still slowest on the road) and got 19.8mpg. quite a difference
I have only driven my on one long trip and I averaged 22 MPG on that trip. I am leaving for another trip for Christmas in Arkansas tomorrow. I will check the MPG then. I have noticed about three MPG difference between crusin' around 60 (backroads) and 75 on the interstate....