I have an 04 Hemi Ram and the manual says to use 89, but you can use 87 as it will retard the timing to compensate. I tried all the grades to test the mpg and didn't see a whole of difference, especially when compared to the difference in price of the fuels. So, I mostly ran 87 for my day to day 45 mph commute driving. That's where the truck lives 99% of the time. On the few occasions I towed with it, I used 89.
That being said, my Hemi dropped a piston 700 miles from home this past summer. Praise the Lord, it did get me home, where I then took it to the dealer. It was 4K out of warranty and the dealer would not do anything, nor would the zone rep, nor Chrysler. I called the 800 number and got all kinds of promises, but in the end they wouldn't do anything. I let that particular dealership do all my customer pay and warranty work on 2 vehicles. I also buy a lot of parts through the parts dept. No offers to split the cost of repair, nor help with trade-in on another truck(they knew I was looking for a diesel). Nothing, just pay us to fix it. I was and still am very disappointed in the lack of customer service.
Well, I took it home and put a used Hemi in it. Upon tearing down the old Hemi, it had suffered from pinging and one of the pistons had a hole in it. I never heard it ping, and I'm very sensitive to that kind of thing. I can only guess that the sensors that were supposed to retard the timing weren't working correctly. Maybe it had been that way since day one and it eventually took it's toll. Maybe it happened all at once. I don't know. I feel it was a mechanical defect that shouldn't have happened and Chrysler should have stood behind it. So, the moral of this story is run the 89 most of the time, or you could end up like me and put an engine in it. That's all I run in the replacement engine. Now my Hemi is NOM!! LOL.
