The funny thing is the 6.1L is one of the few engines that the auto journalists are either able to meet or exceed the EPA ratings on. C&D got 19 mpg, these guys got 21. I know that with the LX sedans, some magazines were getting better mileage than they were with the lighter, more aerodynamic, smaller displacement, AFM featured (their version of MDS) Impala SS/Grand Prix GXP that was rated for about 27-28 mpg.

I'm not sure about that, but if they mean they are not running premium, they are probably taking a risk that they shouldn't take.