For those about to "knock"......
 

Serious question about custom tunes. I ordered 91 performance and tow tunes thinking it is the option for maximum performance. Ford on the other hand says 91 octane is definitely the wrong fuel for my truck. :shrug: I have no clue as what to believe but they swear it can potential do more harm than good. Anyone care to derive an educated response to this? I am like so over learning the hard way! :throwup: The service tech told me I need to be running 87 octane w/ an occasional booster or top off with 91. In either case, can someone tell me why I was'nt informed prior to ordering my custom tunes? Now I feel I have to have Bill or Cody change them over to 87 custom performance and 87 custom tow. :cursin: :censored1: Can a moderator please cue Bill, Corey, or Cody into this and see if they are willing to help me? Also, they said it was a factor in the plugs going bad because the fuel burns too slow. :hmmm: Thanks in advance to anyone kind enough to shed light on this subject. :shocked:

Bill has been doing this for years, and I would be almost willing to guarantee that he has heard of this before. yes our trucks are designed to run 87 octane, but he knows how to advance the timing and other setting to compensate for the 91 or 93 even.
There are a few people on the forum, including me, that just get the 87 because that is the recommendation from ford, and it is cheaper, but i have never heard any problems with plugs or knocking using 91... and I thought higher octane prevents knocking since knocking is when the gas detonates too early :)
so dont freak out unless something bad happens, and if you are in doubt then you can switch back to canned tunes until you get them switched back to 87 if you feel the need to go that way :)

I assumed Bill had dealt with this before. I am just getting tired of having to fix or repair things that normally don't need it. Inasmuch as I want the most power readily available I also MUST have my truck running smoothly. I sure do appreciate your feedback. How does your truck run on 87 custom tunes, although our trucks have different mods? On my programmer, there is no longer canned tunes! :'( All I have is the transmission only/performance/tow. Do they charge you to have the octane part of a custom tune changed? Probably, huh!? (and as an ending thought, my truck runs great right now)!

The reason they said you should only run 87 is because that is what the truck is tuned *from the factory* to run. Anything over 87 isn't going to do much because nothing will be advancing to take advantage of the more stable fuel. Topping off with 93 ever so often is to help boost poor grade fills.

Your custom 91 tune is written to take advantage of the improved fuel grade with features like (but not limited to) timing and cam adjustments.

I dont know how reliable the techs are over there but around here a single oil change can cause your engine blow faster than a blower and a lead foot. Over here they like to make you a return customer.

Thanks Longshot.

Read what he said, hampsterzone.

I have been a dealer tech for the better part of 10 years and I will tell you with absolute certainty that there are some techs who shouldn't even be checking air in tires. Your guy is one of them.

However, there is little to be said about the different "grades" of fuel except that just because it's "premium", doesn't mean it's higher quality. "Premium" is simply a name that the fuel stations give the fuel....maybe to sell more of it for no reason....who knows? The octane rating is (in the simplest terms) the fuel's resistance to detonation. The higher the number, the slower the burn, and the more controlled the flame propagation is across the top of the piston during combustion.

Running 91/93 octane in your truck with stock programming is a waste of money, simply because your truck's stock programming is not able to recognize the "knock resistance" of the fuel and the ignition timing will be far from optimal to actually use the slow-burning traits of the fuel.

Poor fuel economy and sometimes high engine temperatures can be attributed to using higher than recommended octane fuel because once the ignition takes place, the slower burn of the high octane fuel causes the cylinder pressure to remain lower and occur later in each of the piston's travel. As far as hurting the engine? Not likely at all.

Rest assured, young grasshopper, that the ignition timing has been adjusted to make better use of 91 octane fuel. There's not any appreciable difference in different octane fuels, so just because there are "grades" from 85 to 93 out there, doesn't mean that any one is better or cleaner than another.

Excellent answers my friends! I truly do appreciate the "honest" feedback! In addition to your explanation of octane ratings, what would you recommend I run in my truck? 87 octane is definitely cheaper by far around here lately. With that being said, what should I do with my custom tunes? Change them over to 87 because there is not much difference or keep the 91 custom tunes because they are superior and worth the extra money to run the higher octane? And lastely, how much would it cost me to have the tunes changed over to 87 octane on both tunes if in fact you feel I should switch? Thanks in advance, you are awesome!!!!!!

I'm going to add one observation about your tech's telling you that the high-priced juice caused the plug failures. It DIDN'T! The problem is most likely a result of the non-Motorcraft plugs having just a tad different heat dissipation capability. This will either cause them to run hot (which burns the electrodes) or cold (which tends to cause fouling).

There's really not just a whole lot else that can go wrong with a plug. It's not exactly rocket science.

And, yes, your truck WAS designed to burn 87 octane gas. I personally think using 91 or 93 is overkill, but it won't hurt anything. You SHOULD get somewhat more power out of 91 octane, since Bill has adjusted the fueling and timing for it, but he can't adjust the compression, which is what the high-priced stuff is really designed for (a higher compression ratio).

If you had a blower, you'd want to use premium.

There's nothing else in "premium" gas that helps or hurts an engine except the slower burn and resistance to detonation. Premium is actually harder to ignite!

- Jack