Say you have two tunes set up, and the only difference between the two is that one is for 87 Octane and the other is for 93 Octane. Would switching back and forth between the two tunes (assuming you don't do a heavy mix of both octanes at the same time and use the correct tune for the correct octane) at either regular or irregular intervals harm the engine, or anything else?

 

just make sure you have the right octane for the 93 tune. if you run the 93 tune with 87 octane you will experience detonation and could harm your motor. you can switch tunes as much as you want it doesnt hurt the computer.

i have heard that some ECM's can only be flashed a certain amount of times but mustangs are not one of them. my subaru is one of the makes that has this problem with early flash devices but tuners have found a way around it.