I've not seen the 'suggested MPG' ratings for the two engines in the '08 CTS; can anyone help me?

I think I read that the DI is actually supposed to be capable of getting a couple more miles per gallon in highway driving than the base engine. At least that's what I read in a magazine article. But I strongly suspect that any gain will be wiped out by the heavy right foot of the DI drivers. Ha ha. So in other words, it's basically a wash. My window sticker for the base engine states 18/26.

Hey, thanks for the response; I have the DFI, and the window sticker also says 18/26. And, you are right: it's hard NOT to put the 'pedal to the metal' with this engine... Love the sound when I do.

I do a 150 mile round trip in my car once a week, all on Interstate Highways; at 70 mph I usually average 27 to 28 mpg, depending on wind, temperature, etc.

27-28 on the highway is very respectable. Especially on regular unleaded. Between my Corvette and Jaguar S-Type, that both require premium, I was getting a little tired of that. I went with the base engine on the CTS, because when I want to go fast, I'll drive the other car. I know what you mean about the great sound when you get on it, though. I have that "problem" with the 'Vette. I'm somewhat addicted to driving that car as it was meant to be driven - using common sense and when on the streets, within local speed limits, naturally. That doesn't mean I can't get from 0-speed limit fairly briskly, though.

Wow, you guys are doing better than me. Way better. While I do OK in town about 17 and change, I have never gotten over 23 and change on the Interstates. But I only have 875 miles on her, maybe when she gets fully broken in....... On the other had, manufacturing tolerances sometimes all go in one direction and it could be that your engines are a lot looser than mine from the get go.

Drove to Virginia last week. 340 miles one way. Avarage fuel economy 27 mpg. Not bad. Coming back - similar numbers. I am happy.

Those figures are really good :)

I have another post "First Oil Change".......... heading on a 3000 mile round trip to Key West Flordia. I will be keeping a log the old way with miles and fill-up gallons used, plus checking "driver info" on the car to see if it's on the money. I'll try to keep all posted. If I get 27 like posted above, I will be happy. :thumbsup:

BTW, I have the 263hp motor w/RWD.

I got better mileage on an 04 big box DTS than I can get on the DI RWD. Only have 3500 miles but haven't got better than 22mpg of gentile highway driving in TX/OK/KS. I can normally meet or exceed EPA ratings.

If you think about the 10% mileage loss due to the ethanol we all must now run, the car would be right at 30 mpg, which is pretty darn good.

Wow, you guys are doing better than me. Way better. While I do OK in town about 17 and change, I have never gotten over 23 and change on the Interstates. But I only have 875 miles on her, maybe when she gets fully broken in....... On the other had, manufacturing tolerances sometimes all go in one direction and it could be that your engines are a lot looser than mine from the get go.

When I took delivery, I took a road trip about two days later. Over the first ~600 mi of flat interstate driving, I averaged ~23mpg. Last week, I averaged 28mpg for 300 miles w/ slight hills (odometer at 3700 mi). During the first road trip, I did vary speed to help break in, but I assume that was not enough to cause a 5mpg difference. I think once you get a few thousand miles, your mpg will increase significantly.

Not THAT would be sweet! Not that unusual either.........

I an currently getting about 18.5 MPG on the DI engine. I do a 60 miles a day commute into Miami traffic, so I would say some city some highway driving. (4k miles so far without any road trips). On my last CTS('05) I was getting right around 20 mpg as is my wife on her '07. I don't know how much more the '08 weighs thn the '07 which could account for some of the difference in the mileage. Its a little dissapointing but hey,whats the big deal.