2015 Chevy 2500

[Troy R]

Question, I’ve read the Diablo tune would be best with 93 octane for towing my fifth wheel in my 6.0 l. So when I get where I’m going can I drive around in that tune or change it? Do I still use tow/haul mode?

[06MonteSS]

if you put 91/93 octane gas in the truck, then use the Diablo Tune for the ECM/engine tune, and the Firm Shift tune for the TCM/tranny tune...

If you put 87/89 octane gas in the truck, then use the 87 Octane Tune for the ECM/engine, and the Firm Shift tune for the TCM/tranny tune...

You'd still use tow/haul mode like you normally would... That tells the TCM/tranny to use different shifting settings (shift points) for towing.