Originally Posted by vertrkr
Higher the octane the less energy density (BTU) gasoline will have which leads to reduced mpg. Granted it's not much but that's how it works. This can be overcome by advancing the timing but I don't know if Chrysler designed the ECU mapping to take advantage of higher octane fuel that it's designed for, it doesn't sound like it from everything I've read. It will retard the timing if you use lower octane AND it senses pre-detonation (knocking, pinging) but that will reduce mpg slightly when it retards the timing.
Bottom line is the differences are usually so slight you should use what ever grade makes you happy. Unless you hear your engine knocking then go up a grade.
Yeah agree with you, 87 does have more energy content than 93 and the additives/detergents packages for 87 and 93 are the same. The marketing on gasoline commercials always makes me laugh as if the higher octane number is always the best choice. 93 is only better if your vehicle can make use of the higher octane, the additives and detergents are the same as 87 just that the 87 pump doesn't have all of the bight paint and the word super power written in huge letters all over it. 87 runs just fine in the 5.7L for tooling around the suburbs in a normal climate, jeep runs great on it with plenty of power. If you regularly towed 7200lb trailers up mountains in Death Valley when it is 110 degrees some extra octane would probably do you some good. The words to always lookout for are "recommended" or "required". If premium is required like for SRT then you must use it or you will likely cause problems in the engine. One of my past cars was a maxima and it recommended premium which I often used but I could never see any reasonable difference in power over 87 the only thing I noticed is that on highway trips it consistently got 2 mpg less using premium. Not really a cheapness thing I could careless about a few extra dollars a tank, I just don't see the difference or benefit. But to each his own everyone is in a different situation and uses their jeep for different things if 93 makes you happy then use it if 87 does then use it, its all good