So I currently have my 87tune from brenspeed on and want to change to the premium tune, so I know I must run through a tank or two of premium gas. Im wondering if I will be ok loading the new tune on after only running through one tank of premium?

 

i never even ran through a tank, just let the car get low on gas then filled up on 93 and then loaded the tune.. everythign worked great.

 

same here. i ran it down till it said 5 miles left on the computer, filled it with 93, and loaded the tune. no problems.

 

I concur with what was said above. What tune are you loading? If you're going with an 89 or 91 tune and can get 93, then fill up with 93 after the tank gets low and load the 89 or 91 (if you're worried about it). You'll be at or above the octane of either. Whatever octane you're going up to, mixing it with 2 or 3 gallons of a lower octane won't hurt unless your tune is on the hairy edge.