Questions about octane and canned tunes

[Longshot270]

Originally Posted by Skip_1074

Okay, so here it goes...I just purchased my truck and a CTS to go with it. At this point I am not getting any custom tunes on order for at least a few weeks as I have some other things that I need to buy for the truck as well right now. Can I run the 93 performance tune with 87 octane until I am ready to place my order for custom tunes or should I stay with the 87 tow tune?

I am planning on getting both custom performance and tow tunes for 87 octane in the near future, but am trying to make sure that I am squared away until that point.

Thank you.

NO!! The 93 performance tune is specifically for higher octane gas. Doing so could result in damage to your truck.

Use the 87 octane tow tune or fill the tank twice with 93 before switching to the performance tune.

[Jackpine]

X2! (What he said!) Perfectly stated, Longshot!

- Jack

[bigterp]

I have an '07 but I'm sure the same applies. I'm waiting on my gryphon cs to get here. (stuck in the crappy weather in GA for now). But when it does I should run 2 tank fulls of 93 before switching to the performance canned tune? I would think the same would apply once I get my custom tunes (87 T & P, 93 P). How about going from a 93 performance tune to an 87 performance tune?

[Longshot270]

You want to run two tanks of premium before switching to the premium tune because there is 87 in the fuel lines and tank. The first batch of 93 is contaminated with 87 octane fuel. If you go to the gas station when the arm is on E you still have a few gallons left. You will only be diluting it with 93 octane, not replacing it. You will also have pure 87 octane fuel in the gas lines. If you load up the the 93 performance tune and drive agressively with 87 it can very easily cause problems.

The more 93 you add the more you will dilute the 87 octane. Then when you fill your second tank you should have the 87 diluted well enough to not cause trouble.

No problem in going down, you just have to be careful going up.

[Jackpine]

I've determined that my truck still has 5 gallons in the tank when the low level light comes on. So, after driving the truck home from the gas station to clear out the lines of the old fuel (7 miles), I'd determine the actual octane in the tank this way:

((5 x 87) + (25 x 93)) / 30 = 92

I think, really, you could probably switch to the 93 octane tune at this point without too much danger. Don't push the truck hard till you refill the tank with 93 though.

- Jack

[bigterp]

Originally Posted by Longshot270

You want to run two tanks of premium before switching to the premium tune because there is 87 in the fuel lines and tank. The first batch of 93 is contaminated with 87 octane fuel. If you go to the gas station when the arm is on E you still have a few gallons left. You will only be diluting it with 93 octane, not replacing it. You will also have pure 87 octane fuel in the gas lines. If you load up the the 93 performance tune and drive agressively with 87 it can very easily cause problems.

The more 93 you add the more you will dilute the 87 octane. Then when you fill your second tank you should have the 87 diluted well enough to not cause trouble.

No problem in going down, you just have to be careful going up.

Thanks for the response. And sorry for hijacking your thread OP!!! So I can SAFELY run 93 octane with the canned 87 tune for a few tanks before I switch to the 93 canned tune??

[Longshot270]

Yes