I have custom tunes through PHP. I run my 89 tow all the time and now I am making the switch to the 93 performance. My question is if I fill my tank with 93 and run that tune for a while and want to switch back to my 89 would it hurt anything buy running 93 octane on a 89 tow tune.

 

Hi there!

Nope. No problem at all! The fuel octane level can always be higher than the program for which it was written, but you CANNOT go the other direction or you risk detonation.

 

You can run the 89 tune but you need to bump th timing up +2.0

 

Corey and Bluejay thanks for the answers that is what I was looking for thanks for your help.