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Most people run 87 except for the paranoid ones who run 89 or the placebo effect users who run 91.
It could have also been the truck breaking in too.
You say that now until everything is caked in carbon from using 100% gas.
Now try a tank of 87 or 89 and see if it changes. On a stock vehicle running 93 over 87 will get you worse mileage and power, the exception would be if it was pure gas, you would gain a little bit of mileage but still lose power.it also could have been the fuel
to see an instant 1.5 jump in MPG in about 1/2 tank of 93... on the 2nd tank the truck ever had... It started out at 10.5mpg on the original tank (and stayed there) and it actually went up to 11.5 -12 shortly after a 93 fill up. then it stayed their for over the first 1500 miles.
To me it sounds like the majority of it is due to fuel.
EDIT: note that my Manuel recommends 89 min (87 acceptable) thats another sign.
Ok, on a stock vehicle that recommends 89 the same thing applies, you lose power and mileage going above that. Your main point though has never been answered though. My 2014 manual says use 87, it says nothing about 89, they changed it for 2015 and never explained why.
I'm not sure what you are trying to say. I never said anything about your manual recommending 93. I'm more saying if you tried 87 or 89 now you would probably get the same mileage if not better than the 93 you are running. I tried running 93 on the stock tune and 89 stock and noticed no difference in anything aside from the slight drop in mileage.
