The manual recommends 89 octane in the 5.7 Hemi but says 87 octane is acceptable, what are you all running? I am new to the 5.7 and have not yet run my truck hoping to run it on 87 octane.

I have always run 89. 91+ when towing. I'm on my 3'rd and traded the last one at 165k. The engine ran as new.

On 87 you are depending on the knock sensor to take timing out to protect the engine at high load or high temps. Apparently it doesn't always work however, as there have been several reports of holed pistons on 87. Also less timing can increase fuel consumption.

There is a recent post running on this... if you get search to work you will see more opinions.

Other post

https://board.moparts.org/ubbthreads/show...rue#Post7883462

Hmmmmmm....I've gotta 03 and a 08 hemi and never put anything other than 87 octane. I'm not saying that's a good thing though.

I run 87 99% of the time. I've never heard any signs of detonation. I've tried 89 and 91 and couldn't tell any difference except a thinner wallet.