Custom tune question

[Jackpine]

Originally Posted by Northern Supercrew

yep, clear as mud lol. my understanding is that you could run the highest octane in you area on the 93 canned tune..which happens to be 91 in my area. basically, no octane less than 91 on the 93 tune....but that's another rant i will burn the remaining 91 out of my tank and go back to 87 on the 87 perf tune again.

Ah - I think you COULD be asking for a bit of trouble using 91 octane gas in a truck tuned for 93. The timing will be overadvanced, and you should probably retard it a bit or set the tune back to 87. I wouldn't worry too much though, just don't "hammer" the truck and I imagine all will be well.

But, in the future, I'd try to match the octane you put in with the tune you are using. Don't fill with an octane below the tune rating.

Ford even talks about this in the owners manual. They say not to use 86 or 85 octane (in areas where it's available) since the engine is "stock" designed for 87. If 87 is not available, they say to use 89 octane. (Use gas with an octane rating that is equal or higher than the octane the engine is tuned for).

- Jack