I just bought a Diablo Predator for my '08 V10. I am currently running with it set on the 87 octane tune. Will I run too lean if I bump it up to the mid tune? If I do run lean, what will I hurt?

Thanks

 

So by "MID Tune" you mean 89 octance tune right? Say for instance you run a 91 octane tune with 91 octane fuel that by itself has nothing to do with running lean or rich. You want to use the octane fuel that the tune is made for. You want to use a 93 octane tune with 93 octane, and 87 with 87 octane an etc. If you run 87 octane with an 89 tune you will probably get pinging and decrease performance. The higher octane the fuel the more spark advance you can put into it without getting ping or spark knock. When Diablosport made the canned tunes for your tuner they took a stock 08' V10 put it on the dyno and made the tunes up for it, so the A/F ratio should be just fine. Diablosport actually probably enriched the A/F ratio with their tunes as in stock form Ford tunes their engines on the lean side especially during decel.

 

There is power to be had leaning engines that don't have forced induction.