Is there a big difference in the gas mileage of an STS vs. an SLS version of the Seville?

Is there a big difference in the gas mileage of an STS vs. an SLS version of the Seville?

Short answer : NO

The engine is the same the transmission is the same, the weight of the car is the same! The only difference is "tuning" or exhaust (275hp vs 300hp).
i would expect 1mpg at MOST.

IMO the SLS is like a regulaer C5 coupe..the STS is more of a Z06...but back to subject i would think they get the same gas mileage :?

Only differences is the cams and the final drive ratio. The computer is ovbiously calibrated for the differences between the two cars, but not really anything that affects the mileage.

Yeah, the STS has a few more luxury appointments, and has a bit more power - but all in all - same car in re milage I believe.

If there is a difference, its 1-2 mpg I would think.