Regular is fine per the manual. I know it's not super scientific but I tried higher octane fuel and it performed the same and my mpgs were pretty much the same. I would think the only way to have benefits of using higher octane fuels would be to have it tuned to run that.
I go with 93octane. My truck is NOT a daily driver so when it sits all week I like to know it has good fuel in it. I feel it runs better on it as well. less knocking from the valves. sometime when you get shitty 87 octane you tend to hear different noise in the motor. Also when I mash the throttle on my truck never any hesitation. I will always continue to run 93 octane. I don't care what dealers or people say.
The octane debate always gets me. This is obviously not scientific and I'm only guesstimating, but let's put this into perspective. Let's just say the difference between 87 and 89 is .15 cents (I think it's typically less). And let's say you have the 23 gallon tank. Filling up once a week, you are looking at $179.40 a year. At that equation you are looking at a difference of $3.45 a fill up. You paid about $50k plus on your truck. Are you really worried about less than $200 a year for optimal performance as stated by the manufacturer?
I'm opting for optimal performance so I put in 89.