The 11 cars now available in September's Pennzoil car pack for Forza Motorsport 4 are all pretty ... slick. For 560 MS Points ($7) you'll get a couple of Vipers, an Alfa Romeo 33 Stradale and a '53 Corvette, just to name a few. The full list of the cars can be seen past the break.Players that picked up a season pass for the game will have to shell out money for this DLC pack, as the last add-on to be included in the pass launched in April. New Community Monthly Rivals Mode events, including one that features the Pennzoil-sponsored Vipers, accompany this new release.