I've done some research into the trans fluid used by Chrysler dealers for the older 300's and Chargers with the 5-speed NAG1 transmission. Seems that they all use ATF+4. Also, I've heard that Valvoline supplies Chrysler with their Mopar ATF+4. From this info, it would appear that it's OK to to use ATF+4 in the Crossfire NAG1 trans. Anecdotal reports support this conclusion.