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I just got my charger and was wondering what grade octane is best? Its a 5.7L hemi. What do you use? I read that dodge recommends 89, so thats what I have been running. Is running a higher octane bad for the engine? Tell me what you think...
 

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89 octane is correct. Using a higher octane while stock offers no benefit.
Those running 91 or 93 octane performance tunes are using the Predator.
 

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I just got my charger and was wondering what grade octane is best? Its a 5.7L hemi. What do you use? I read that dodge recommends 89, so thats what I have been running. Is running a higher octane bad for the engine? Tell me what you think...
I won't tell you what I think. I'll tell you what I know.

Summary is this: run what you're supposed to run. Higher octane does NOT mean "more power". Higher octane means "more difficult to ignite". In layman's terms, what you don't want is a fuel igniting earlier in the engine cycle than is intended. That causes knock, which is bad. You don't want the air/fuel mix to ignite while the piston is still coming down into the cylinder, during the compression phase for instance. You want it to ignite when the piston gets to the bottom of its travel, so all your force is pushing it back up.

The electronics of the 5.7L Hemi are designed for 89 octane. It can adapt and run on 87 octane by adjusting its internal timing. The fuel may detonate earlier than expected, but knock-sensors will notice this and "retard" timing to compensate. End result: less power. Not because your fuel has less energy, but because your engine has adjusted its timing to adapt to fuel that ignites easier than it was designed for.

So. What happens when you throw 91 or 93 or 94 or 100 octane fuel in your engine? Nothing good. The fuel is harder to ignite than the controller expects. That's it. The 5.7L is designed for 89 and doesn't adapt in any way to higher octane. You just spend money, for no benefit.

As has been mentioned, there are programming devices such as the Predator that change the engine controller so it advances timing, requiring higher octane fuel, to squeeze a little more power out of the engine. Again, it's not that your fuel has more power, it's that the timing is adjusted and THAT results in more power.

I run a 91 octane tune (Predator) in my 5.7L. Obvious increase in performance. But if I didn't have the Predator, I'd just be throwing my money away.
 

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Unless your running a predator, 89 is fine.
 

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Unless your running a predator, 89 is fine.
Sorry, but I'd like to rephrase your answer SupremeG. It's not fine. It's correct. Also know as ideal. Some readers might interpret fine as "good enough", imagining there's better-than-good-enough to be had with higher octane fuels.
 
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