I agree because I bought a reg. cab 5.0 for street performance and 91 is better for it and the engine overall.I'm running Mobil 91 Octane.
Expensive.
My mind and wallet say, If it doesn't knock on top tier (additives) 87 its probably fine.
But I love my 302 so much I just cant bare to put anything less in it yet.
It would be nice to know what the 'lesser' brands are but who's going to pay for that? VS them paying to have their fuel certified and more people willingly pay more for better quaintly. I kid you not, I gain 3 mpg in my Ram 2500 by switching from Sam's club to Costco. I only run costco 83 and I get 21/22 highway in 5.0 doing 70-80. That Ram got the same MPG with speedway gas...When I had my short bed 04 Hemi I had a difference in performance between the different octane levels. As far as top tier gas I would like to see a study stating the brands of lesser quality. I think you will find there is no suck study. Gas is the same only the additives may differ.