I've been running 87 in it since I bought it, no knocks (not even on startup or under hard acceleration). Mind you, I have just over 3k on it, but those would be the times when the engine WOULD knock. There is really no reason for those of us with the base or limited models to run 93 or 94, unless you want to squeeze every little bit out of the engine. Now those of you with the SRT-6 should run the highest octane you can get your hands on. Anything that runs compressed intake air needs the slower detonation the octane provides due to the enhanced compression. If you have any type of boost, the fuel-air mixture will ignite too quickly and will absolutely damage the engine over time, and your performance will be noticeable different (I used to drive a turbo back in the day, couldn't get out of its own way on anything less than 93). For the normally aspirated engines, 87 is fine as long as it doesn't ping. Carbon? Run some BG through it every once in a while, or fill up with premium on occasion. Most gasoline's now have soooo much detergent in them, carbon isn't really a problem.