Chrysler's 6.1L Hemi is reserved solely for SRT models, and produces 425 hp from just 370 cubic inches. All this power does come with a cost: a gas guzzler tax, and a combined 13/18 mpg (hwy/city). Unlike its smaller 5.7L stablemate, the 6.1 does not have the Multiple Displacement System (MDS), which shuts down four cylinders at cruise. The addition of MDS would improve economy by some 10-12 percent. Rumor has it that the standard Hemi will get a bump next year to 380 hp from its current 340. Look for that improved plant in the forthcoming Challenger R/T.