I have always ran Shell or Amaco because they are usually the only brands that don't add ethynol, which over time will dry out rubber and start the decaying process. I learned this several years ago from a small engine mechanic because I kept having trouble with my weedeater and chain saw. Three years later, not a single bit of problems with them. Obviously, a car engine isn't affected nearly as fast or is as noticeable, but it will eventually have an affect.

I have an '03 5.7 Hemi with a CAI. I went ahead and ran a tank of 87 and did notice a slight difference in acceleration. I may try a tank of 93, but everything I have always read said it was a waste of money to run a higher octane than what the manufacturer states.

Thanks for the feedback.

 

Some have had some problems when they ran 87. But is it really worth running any risk when its only an extra 2-4dollars to fill for 89?

 

I chipped my truck @ 300 miles and I've never used anything but Mobil 1 every 3k miles along with 93. I think if I were to start using it now the truck would knock, although I do have other motor mods, so yea, that's my reason for the 93.

 

I ran 87 with no problems until I chipped my truck.
Now that I have the Superchips, I run 91 or 93 octane.

 

I have only ran 85 in my 05 hemi. Never heard any knock or anything. it runs great. The truck is stock except for the flowmaster exhaust and my engine oil is amsoil. Soon my whole drivetrain will be amsoil.

 

Running a higher octane doesn't really help. Lower octane I'd recomend regular at the lowest. It is just because there is a knock sensor and the computer allows for fluxuation in the timing. Higher octane lets it run a more agressive timing and lower octane retards the timing. Oil shouldn't really make a difference on if it knocks or not. If it's knocking because of a different oil, it's not because of detonation. Synthetics are better for older motors with blow by because it resists being diluted by fuel from the blow by.