I'm about to install my JLT/XCAL combo that I got from Doug! I'm installing a 93 performance tune, but I still have about 1/8 tank of 89 octance in my car. Will it be ok if I run the 89 out and immediately switch to 93? Do I need to fill up with 93 a couple of times before I load the tune?

 

I would be safe and run the old gas out before installing the 93 tune.
Did Doug give you a 87 or 89 tune to run with the JLT also?
You could do that and fill the car a few times with 93 before you switch the tunes.
Just my 2 cents.
Steve

 

You are safe, that is as close I came and my tuner was not concerned.

 

At 1/8, you should be able to fill it up with 93 and be safe. I have had about a half a tank of 87 and half tank of 93 (during hurricane shortage last year, could only get 87) and I could hear a little pinging at WOT, so it does make a difference. But you should be OK.

 

I ran mine to 1/8 and refilled with 93 and ran it till 1/2....Just to be safe. I mean how much of a delay could it be.