The 2011 Audi A8 has the same engine as the S5 although it is quite a bit larger and 500 pounds heavier. Yet the A8 has more horsepower (372) vs. the S5 (354). Also the A8 gets better gas mileage (17/27) vs the S5 Tiptronic (16/24). With the S5 being a smaller, sportier vehicle it should have at least the same horsepower with much better gas mileage. Audi is doing a great job, but needs to re-visit this one. Hopefully it won't be a V6......