I use 87 99 % of the time.The Hemi loves it . I only use 89 when I'm towing my boat. And then I only put in what it will hold, o it's really not all 89. The truck has no problems As for the dealer saying that you broke the warrenty for using 87, The only way they would know that is if you tell them that. There is no equiptmentat Chrysler has that can tell the Ocane in your tank. If they say they can tell ,there lying I worked inthe Octane testing business for eleven years before retiring and I've seen a lot of new stuff for testing octine and none of it works. Thae is only one way and that is the ASTM Method.

 

I recently got the SP tuner and had it set toeconomy (87) tuning. Ran 2 tanks and I am getting around 12 mpg. Going to switch to premium today and change the tuning and see what happens. From what I am reading though it looks like the performance setting is going to to better for me.