I installed the SCT tuner, using 87 octane tune. Changed tire revs for the installed 20's. Didn't mess with axle ratio, rev limit drv or Neu, Idle Speed Drv or Neu, wot sifts points. Didn't know which options were best? Any suggestions.

2012 Screw EB FX4

 

Options best for what? What do you want from the truck? Drive it with the 87 and see how you like it, then switch to the 93 ( with full tank of 93 octane fuel of course ) and see how you like the difference.

 

Will it matter if I ave 89 octane instead of 87? I will go to a full tank of 87 when this tank is done. I know going lower is a no-no, but will higher harm anything? I want better performance and MPG out of my truck. Since the 20's don't get me that 22 highway driving a steady 70-75.

 

No, you can always go higher on octane fuel in truck then tune, just never want to go with lower fuel then octane tune.

 

Why?

 

Try it and find out. You don't want to run low octane gas on a higher octane tune. Detonation will ruin a perfectly good engine