I searched and couldn't find this discussed already. The owner's manual says 87 octane is acceptable and 89 is preferred. So when I first got my Charger Daytona 5.7L I was using 87. Since then an article was published in Car and Driver magazine where they compared performance differences between the different grades of gas, as it relates to several cars, one of them being a Charger R/T with 5.7L engine. They found that the performance hit was minimal when using 87 octane gas and the savings were significant. It's hard to argue with these findings. However, I notice a big difference in performance and drivability, not just between 87-89, but also between 89-93. 93 seems to be the ideal, running smooth like one would expect a modern fuel-injected engine to do. With 87 or 89 there seems to be some hesitation and/or frequent lulls in power delivery. With 93 I can "light 'em up" any time I want. 87 and 89 seem to be slower off the line. Opinions?